Corvette 700R4
 

Do they have a traditional trans mount in addition to the C beam mount, or just the C beam mount? And if only the C beam mount, is it easily changed/worth changing the tailshaft housing if you get a known good transmission?

Yes it has a C beam mount and yes you can easily swap the tail shaft housing. If your using a aftermarket torque arm with it, who cares if the tail shaft housing is different. Unless it is a trans mounted torque arm.

Potentially Would not be going into a 3rd gen so it would need a regular trans mount

Gotcha. But if I remember right. It's been err 9 years since I've researched this, the vette tail shaft still has the trans mount in the same spot.