LSX 454 and a 6L90 in a 72 k5 blazer

[Luba]

I am planning on doing a frame off resto of my 72 Blazer. I would like to run a mast motorsports LSX 454 fuel injected small block (700 hp) and a newer 6 speed tranny and put it into my k5. I already have a dana 60 front, 14 bolt rear 4.56 gears detroit locker in the rear, maybe an ARB in the front. I know the mast ecm will control the 6l90. I plan on running around 37" tires and want to be able to drive this thing anywhere. I plan on fully boxing the frame and building a cage tied to the frame. Just wondering what kind of power levels the 6 speed auto can handle. Also wondering if I can bolt my np205 t-case to it, or if I should get a different one. Any advice?