T56 Swap to T56 Magnum

[Nitrous]

I have a 69 Camaro that was an original 350 with an auto. The previous owner took all of that out and dropped in a h/c/i LS1 with a T56. The engine is making 475hp and I have plans to add a power adder (supercharger or TT) in the next couple years to push it to 750+. The T56 in it now needs a rebuild, reverse is now almost completely shot and I can't shift above 5k rpm. I'm thinking I might swap it out for a T56 Magnum and sell this t56 as one to be rebuilt if anyone wants it.

My question is, I know that the driveshaft will have to be shortened but will I need to do any other modifications? Will the transmission cross member have to be replaced with a different one? Will the shifter be in the same location or will I need something to adjust it? Will the transmission tunnel have to be modified?

Any help would be appreciated.