Kevin and Pete,
You guys are evil and Kevin I know you enjoy it. I am thinking the way to tackle this is to buy the kits and make the changes. The price is right and with the mods suggested I think I can have a very reasonable representation of my Brill coaches. Of course he sells the seats separate and I could then scratch build them in styrene and get the correct windows and weird siding.
Thanks both of you for the advice and help. These are high on the priority list. By next September I really want to have my box car, caboose, oil car, two coaches, and the #3 2-6-0 complete for a static display for the 2016 NP convention. The above photos are part of a complete photo of a mixed train with the above equipment. I have the box car done. The caboose is half done, the locomotive and tender are awaiting electronics (not preventing it from being displayed) and a hand rail. That leaves the oil box car and these coaches. So they are on the radar.
I did notice how easy it would be to cut a 13th window into the J&S coach where the stove is.