MISSION: Install ZZ502 into '72 chevy 3/4 ton 4X4

[TheCanadianJedi]

Hello everyone!
Well the title pretty much says it. I just joined the forum and am looking for any advice or suggestions that would help this 350 to 502 swap go as smooth as possible.
Here's the run down:
Current power and drive train are 350ci,700R4,NP205,10.5" corporate 14 bolt rear with Dana 44 up front, 410 gears.
I have heard of firewall clearance issues with this swap but when the 700r4 went in I moved the engine ahead rather than the T-case back to compensate for the longer trans case. It was about an inch or so. Is this going to be enough for the 502 fire wall clearance? Also motor mounts. As it turns out GM never produced a '72 4x4 with a big block so no factory mounts are available???!!!! Can I get away with small block pads and stands? What about header clearance? I've got hooker long tube ceramics.

Absolutely any advice or suggestions on this would be very much appreciated!
Thanks.