I think that Union Station bought the dies for the American Limited cor kits but I have not heard yet if they have started producing them again. The M&R sides are 156mm long. The Kato smooth side cars are 188.5mm so would have to be shortened. I have done that on a few conversions. The old Con Cor smooth side cars are 154.5mm. The roofs would be the tricky part to lengthen but it could be done by using two roofs. The new Con Cor Budd cars are the right length but have corrugated roofs. If you can find them the old ROWA cars are the exact 156mm long.