A short shaft water pump and a 2-sheave pulley will help move the belts back behind the crossmember, but putting a U-shaped cutout in the top of the crossmember and filling it in with a flat plate might make the engine position a little more adjustable.

DO NOT leave the bellhousing area crossmember out- - - -fabricate one out of square tubing and flat plate that will clear the torque converter housing and bolt it into place. That one serves as a stabilizer for the rear spring hangers and you'll get a lot of unwanted frame flex and possibly squirrely handling unless the frame rails are tied together near the spring mounts.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!