Personnally not a transvestite kinda guy, but I understand why people put SBC in most everything years ago and now the LS style/family of engines now.
One concern for me is the major surgery to the transmission crossmember. This is a structural member of the chassis. I would seriously consider constructing another farther rearward to aid in torque control/body stiffness, act as a driveshaft hoop and yet allow transmission removal.
Those 6 liter engines with the "bigger" cam produce a lot of torque, so body flex becomes an issue. Get into the local Mopar crowd and see what the factory big block cars had.
Also I would find an experienced welder to check your welding to verify the integrity. You do not want welds breaking when you get into the loud peddle. Someone in the local car community will have good welding experience. You may need to buy the pizza and beers.