I posted lots of pics of a 518 in an e-body mod in this thread.

https://board.moparts.org/ubbthreads/ubbt...-automatic.html

It should be the same on an 69 B body. With Torsion bars, floor pans, K-frames, suspension and even the rear mount brackets swap-able (or at least nearly swap-able in some cases) between mid 60 to 72 B body and 70-74 Ebody I think it would work. I KNOW THERE ARE DIFFERENCES IN THE PARTS ALONG THOSE YEARS BUT THEY WILL BOLT IN PLACE SO THE STRUCTURE CAN'T BE MUCH DIFFERENT.

Instead of removing the center of the brace I just trimmed the stiffening ribs and some unnecessary mounts of the side of the transmission.

Worked fine for me. Just food for thought.