--- a/lang/english.txt	Sat Feb 04 15:28:30 2006 +0000
+++ b/lang/english.txt	Sat Feb 04 18:25:07 2006 +0000
@@ -2769,8 +2769,13 @@
 STR_REPLACE_HELP                                                :{BLACK}This allows you to replace one engine type with another type, when trains of the original type enter a depot
 STR_REPLACE_REMOVE_WAGON                                        :{BLACK}Wagon removal: {ORANGE}{SKIP}{STRING}
 STR_REPLACE_REMOVE_WAGON_HELP                                   :{BLACK}Make autoreplace keep the length of a train the same by removing wagons (starting at the front), if replacing the engine would make the train longer.
+STR_REPLACE_ENGINE_WAGON_SELECT                                 :{BLACK}Replacing: {ORANGE}{SKIP}{SKIP}{STRING}
+STR_REPLACE_ENGINE_WAGON_SELECT_HELP                            :{BLACK} EXPERIMENTAL FEATURE {}Switch between engine and wagon replacement windows.{}Wagon replacement will only be done if the new wagon can be refitted into carrying the same type of cargo as the old one. This is checked for each wagon when the actual replacement takes place.
 STR_ENGINE_NOT_BUILDABLE                                        :{WHITE}Engine is not buildable
 
+STR_ENGINES                                                     :Engines
+STR_WAGONS                                                      :Wagons
+
 STR_SHORT_DATE                                                  :{WHITE}{DATE_TINY}
 STR_SIGN_LIST_CAPTION                                           :{WHITE}Sign List - {COMMA} Sign{P "" s}
 

--- a/train_cmd.c	Sat Feb 04 15:28:30 2006 +0000
+++ b/train_cmd.c	Sat Feb 04 18:25:07 2006 +0000
@@ -584,6 +584,9 @@
 			TrainConsistChanged(GetFirstVehicleInChain(v));
 
 			InvalidateWindow(WC_VEHICLE_DEPOT, v->tile);
+			if (IsLocalPlayer()) {
+				InvalidateWindow(WC_REPLACE_VEHICLE, VEH_Train); // updates the replace Train window
+			}
 		}
 	}
 

--- a/vehicle.c	Sat Feb 04 15:28:30 2006 +0000
+++ b/vehicle.c	Sat Feb 04 18:25:07 2006 +0000
@@ -1742,6 +1742,11 @@
 					continue;
 			}
 
+			if (w->type == VEH_Train && IsTrainWagon(w) && !CanRefitTo(EngineReplacementForPlayer(p, w->engine_type), w->cargo_type)) {
+				// we can't replace this wagon since we can't refit the new one to the right cargo type
+				continue;
+			}
+
 			/* Now replace the vehicle */
 			temp_cost = ReplaceVehicle(&w, flags);
 

--- a/vehicle_gui.c	Sat Feb 04 15:28:30 2006 +0000
+++ b/vehicle_gui.c	Sat Feb 04 18:25:07 2006 +0000
@@ -464,7 +464,7 @@
 
 		if (!EngineHasReplacementForPlayer(p, i) && _player_num_engines[i] == 0 && show_outdated) continue;
 
-		if (rvi->power == 0 && !show_cars)   // disables display of cars (works since they do not have power)
+		if ((rvi->power == 0 && !show_cars) || (rvi->power != 0 && show_cars))  // show wagons or engines (works since wagons do not have power)
 			continue;
 
 		if (*sel == 0) *selected_id = i;
@@ -520,7 +520,7 @@
 				const Engine *e = GetEngine(engine_id);
 				const EngineInfo *info = &_engine_info[engine_id];
 
-				if (ENGINE_AVAILABLE && RailVehInfo(engine_id)->power && e->railtype == railtype) {
+				if (ENGINE_AVAILABLE && ((RailVehInfo(engine_id)->power && WP(w, replaceveh_d).wagon_btnstate) || (!RailVehInfo(engine_id)->power && !WP(w, replaceveh_d).wagon_btnstate)) && e->railtype == railtype) {
 					if (_player_num_engines[engine_id] > 0 || EngineHasReplacementForPlayer(p, engine_id)) {
 						if (sel[0] == 0) selected_id[0] = engine_id;
 						count++;
@@ -667,9 +667,14 @@
 			* XXX - DO NOT EVER DO THIS EVER AGAIN! GRRR hacking in wagons as
 			* engines to get more types.. Stays here until we have our own format
 			* then it is exit!!! */
-			train_engine_drawing_loop(&x, &y, &pos, &sel[0], &selected_id[0], railtype, w->vscroll.cap, true, false, true); // True engines
-			train_engine_drawing_loop(&x2, &y2, &pos2, &sel[1], &selected_id[1], railtype, w->vscroll.cap, true, false, false); // True engines
-			train_engine_drawing_loop(&x2, &y2, &pos2, &sel[1], &selected_id[1], railtype, w->vscroll.cap, false, false, false); // Feeble wagons
+			if (WP(w,replaceveh_d).wagon_btnstate) {
+				train_engine_drawing_loop(&x, &y, &pos, &sel[0], &selected_id[0], railtype, w->vscroll.cap, true, false, true); // True engines
+				train_engine_drawing_loop(&x2, &y2, &pos2, &sel[1], &selected_id[1], railtype, w->vscroll.cap, true, false, false); // True engines
+				train_engine_drawing_loop(&x2, &y2, &pos2, &sel[1], &selected_id[1], railtype, w->vscroll.cap, false, false, false); // Feeble wagons
+			} else {
+				train_engine_drawing_loop(&x, &y, &pos, &sel[0], &selected_id[0], railtype, w->vscroll.cap, false, true, true);
+				train_engine_drawing_loop(&x2, &y2, &pos2, &sel[1], &selected_id[1], railtype, w->vscroll.cap, false, true, false);
+			}
 			break;
 		}
 
@@ -888,6 +893,9 @@
 				if (WP(w, replaceveh_d).vehicletype == VEH_Train) {
 					// set on/off for renew_keep_length
 					SetDParam(1, p->renew_keep_length ? STR_CONFIG_PATCHES_ON : STR_CONFIG_PATCHES_OFF);
+
+					// set wagon/engine button
+					SetDParam(2, WP(w, replaceveh_d).wagon_btnstate ? STR_ENGINES : STR_WAGONS);
 				}
 
 				DrawWindowWidgets(w);
@@ -919,7 +927,7 @@
 						for (i = 0 ; i < 2 ; i++) {
 							if (i > 0) offset = 228;
 							if (selected_id[i] != INVALID_ENGINE) {
-								if (!(RailVehInfo(selected_id[i])->flags & RVI_WAGON)) {
+								if (WP(w, replaceveh_d).wagon_btnstate) {
 									/* it's an engine */
 									DrawTrainEnginePurchaseInfo(2 + offset, 15 + (14 * w->vscroll.cap), selected_id[i]);
 								} else {
@@ -970,6 +978,11 @@
 			byte click_side = 1;
 
 			switch (e->click.widget) {
+				case 12: {
+						WP(w, replaceveh_d).wagon_btnstate = !(WP(w, replaceveh_d).wagon_btnstate);
+						SetWindowDirty(w);
+						break;
+					}
 				case 14: case 15: { /* Select sorting criteria dropdown menu */
 					ShowDropDownMenu(w, _rail_types_list, _railtype_selected_in_replace_gui, 15, 0, ~GetPlayer(_local_player)->avail_railtypes);
 					break;
@@ -1036,7 +1049,7 @@
 { WWT_SCROLL2BAR, RESIZE_BOTTOM,    14,   444,   455,    14,   125, STR_NULL,       STR_0190_SCROLL_BAR_SCROLLS_LIST},
 {      WWT_PANEL,     RESIZE_TB,    14,   228,   455,   126,   197, STR_NULL,       STR_NULL},
 // train specific stuff
-{      WWT_PANEL,     RESIZE_TB,    14,     0,   138,   198,   209, STR_NULL,       STR_NULL},
+{ WWT_PUSHTXTBTN,     RESIZE_TB,    14,     0,   138,   198,   209, STR_REPLACE_ENGINE_WAGON_SELECT,       STR_REPLACE_ENGINE_WAGON_SELECT_HELP},  // widget 12
 {      WWT_PANEL,     RESIZE_TB,    14,   139,   153,   210,   221, STR_NULL,       STR_NULL},
 {      WWT_PANEL,     RESIZE_TB,    14,   154,   277,   210,   221, STR_NULL,       STR_REPLACE_HELP_RAILTYPE},
 {    WWT_TEXTBTN,     RESIZE_TB,    14,   278,   289,   210,   221, STR_0225,       STR_REPLACE_HELP_RAILTYPE},
@@ -1117,6 +1130,7 @@
 			w = AllocateWindowDescFront(&_replace_rail_vehicle_desc, vehicletype);
 			w->vscroll.cap  = 8;
 			w->resize.step_height = 14;
+			WP(w, replaceveh_d).wagon_btnstate = true;
 			break;
 		case VEH_Road:
 			w = AllocateWindowDescFront(&_replace_road_vehicle_desc, vehicletype);

--- a/window.h	Sat Feb 04 15:28:30 2006 +0000
+++ b/window.h	Sat Feb 04 18:25:07 2006 +0000
@@ -353,6 +353,7 @@
 	byte sel_index[2];
 	EngineID sel_engine[2];
 	uint16 count[2];
+	bool wagon_btnstate;	// true means engine is selected
 } replaceveh_d;
 assert_compile(WINDOW_CUSTOM_SIZE >= sizeof(replaceveh_d));