1972 C20 Big Block Engine Mounts

[traymond73]

New to the board. Basic info before I pose my question:

1972 C20 Super Cheyenne with stock 402 and TH400
Swapping out engine for a 500 HP 468 and 3000 RPM torque converter
The truck appears to have the correct 1972 big block engine brackets.

My questions:
1. Do I need to replace both the engine mounts and the brackets? Or will just swapping out the mounts be enough?

2. My understanding is that the 1972s used a different mounting set-up than previous years. What is that set-up? pictures?

3. After seeing number 2 above, can someone point me to where the correct mounts for 1972 big blocks are actually sold?

Thanks in advance!