Welcome to the 'bolt, Johnny; Interesting project you've got in mind. You'll probably get a lot of different opinions on this one.
Back in the good ol' days, my parents had a '50 Chevy with a 216 and we'd pull an old masonite trailer in places you wouldn't believe (Tioga pass, for one). The key was not to get impatient!
I think the 235 would be adequate, by the way is it a "full pressure" 235? I wouldn't want to use a babbit pounder for what you want to do. The T5 would be a good choice I think and a rear gear of 3:73 to 4:11 should work for you. The 235 can be tweaked here and there to give pretty good torque and the OD should get you down the highway pretty good when you're not pulling the trailer.
