TH-350 to TH-400, different trans mount?

['70 C/10 SS500]

(I know this is in drivetrain, but need some replies fast!)

I'm in the process of installing my Caddy 500/TH-400 into my previously 292 I6/TH-350 '70 C/10. The trans mount from the caddy cross member doesn't look like it'll work with my truck cross member. For reference, the motor/ trans. came out of a '76 Coupe Deville. The tranny is a long tail shaft BOP TH-400.

Questions:
1. Is there any difference between tranny mounts for a 350 vs. a 400?
2. Can I just unbolt my 350 mount, put it on the 400, and relocate the crossmember?
3. What tranny mount do I need to use?