A while back, I bought one of the Backwoods miniatures conversion kits for a SW into a On30 diesel. "Drop right onto" the frame they said on the site. LIES, I found out. You practically had to re-machine each end of the frame. When I pointed this out to the owner, he admitted that was actually the case but made no apologies about it at all. His castings were also deformed just to where nothing was square.
It was a total nightmare to build and a happy day for me came when someone decided to buy the project from me.
In business or not, I wouldn't take one of his kits for free, today.