A piece of unobtanium scored.....

[Chatt69chgr]

I can tell you that the C-body booster on a 69 New Yorker is exactly the same as the one on a 69 Charger with the exception of the actuating rod that connects through the firewall to the bellcrank.  And Prior can change that rod when they rebuild these to be the correct shorter length for a "B" body.  On these two applications the booster mounts directly to the firewall reinforcing plate.  That plate is different between power brake cars and cars that came without power brakes (but the non power brake plate can be filed out to work).  I don't know about Hemi's.  I seem to recall that the booster is mounted some metal pieces that move it away from the firewall and up.  Just like is done on some "A" bodies.