Rebuilding 72 for towing work

[Beyond]

I'd like to fix up my 72 and make it a tow monster for hauling my race car. Since the car's a 71 I think it would be pretty neat them both being from the same era. Anyways, what would you guys recommend for doing this. It's a 3 speed on the tree, 350 that needs rebuilt.

Should I stick a big block in it with say a TH400? Or are some of these newer automatics any good for towing?

How about the coil springs? Mines got those little helper leafs on the back but not really the best setup I don't think for towing. Should I pull those out and use air bags?

Just looking for some ideas, gonna put the ol' girl back to work.