You upped the ante! Disc brakes and a posi on the 3.42 or open and drums on the 3.73? I'd have the 3.42 with discs and live with having to downshift occasionally.
Like you said 2000 rpm is your peak torque, that is why I suggested the 3.73s with 30 inch tall tires, you can still run in 5th at 55. 65 mph will be a nice smooth cruise and should hold speed just fine.
I ran a t5 in my coupe with 27 inch tall tires and 3.38s in the rear with a 54 235, HEI, 2 bbl carb and split exhaust. It would lug in a little bit in 5th around 55 miles per hour if you needed to climb a hill or pass someone. Went to a V8 and automatic.
