If you never intend to soup up either engine and had a good 250 and a good 292 I would suggest the 292 for its greater torque and slightly more HP.
The bad news is the 292 will drink more gas than the 250. More horses eat more hay.
If you have both and they both need to be done over then the 250 is a bit less money as far as block internals go. Bolt on items like manifolds and headers and distributers are common to both engines as are the cylinder heads.
Right side motor mounts are in different locations on the 250 and the 292. The 292 is about 2 inches taller than the 250 due to longer stroke. May or may not present a hood clearance problem depending on the car.
I'd take a free 292 any day even if it was decided not to use it in this project. Someday your budget might be fatter.
