Need a little guidance from the gurus

My advice:

Get a 318 or 360 magnum, install an air gap and a 600-650 cfm carb. Goes right in the car, will make good power, lots of header options, can run a 904, so your shifter will hook right up.

You could use the 360 motorhome engine but the trans may have a companion flange and may be useless to you anyway. You'd still need a kickdown linkage that fits on the car anyway. They are all bound to be pretty low power.

I would guess most motorhomes have Dana 70s or Dana 80's, unless they are really small. You wouldn't want to use those. Probably go with a 94-98 mustang 8.8, A-body 8 1/4, Explorer axle with one side shortened, or a 65-70 B-body 8 3/4 if you can find one and have wheels with a lot of offset.

We are doing a 318 magnum/904 in my friend's 71 Demon. We picked up a rebuilt 318 magnum for $200 on CL, a 904 on CL for $150, and a B-body 8 3/4 with a 3.23 sure grip for $450. With all the incidentals, it's probably another $900 by the time it's all installed. We did spend another $325 for a Lunati hydraulic roller cam for it.