Chris,
I think Matt's advice is really good especially since you don't have a lot
of time before Christmas. You would also be able to use the engine you
just bought. That would also allow you to use many diesels. Just about any
4 axle engine would work I would think. I couldn't speak to how 6 axle
engines would work having never owned one myself. To be honest I'm not
sure if the equipment I have would work on 24" curves or not. The coupler
swing is pretty much maxed out on the 50' cars. If the curves were any
sharper I'd be lifting the inside wheels or worse. One thing I've noticed
that helps is switching to Kadee coupers as they have a little more play
than the OEM Atlas or Weaver couplers.
Geoff