Tom,
I have built 3 of Lionel's single stall engine houses and painted each one differently. Two of the kits were identical and were issued in the 1970s. The 3rd one was a repro issued probably in the 1990s. The only difference in that one was the parts were colored differently. I also built an extra long engine house using parts of two more of the 1970s kits. I will be glad to post a few pictures if you wish. I did very little true kit bashing other than adding a strip of black craft paper to the roof top to represent a roof ridge cap. The 3 standard length houses will be used in lieu of a 3-stall RH. You may notice the unpainted 3/8"X3/8" wood strip on bottom perimeter - I thought I might need a bit more height due to height of track. Will add a 3/8" embossed block strip over it soon.
By the way, got all kits on eBay. They appear to be readily available.