3.73 will work fine. You might want to get a cup of tea...this could take a while as I have a few different scenarios in mind for you. Over the 50+ years I've studied and set up gearing, I've learned two things: most people find 2500 rpm a point at which a gear change "sounds" and "feels" right. For the 1959-1962 235, a shift point of 2500 is about perfect as you've already reached maximum torque at 2000 rpm and at 2500 rpm you have not yet begin the drop-off in torque that will come around 2800 rpm. Torque is after all the important consideration--not horsepower.
The second thing is most people do not enjoy what I've come to call "the cement mixer effect"...meaning it is necessary to shift through three or four gears too quickly because the gear ratio chain is mismatched for the engine and the person is simply trying to get to fifth gear asap. Fortunately you won't have to worry about that, but friends of mine who have simply bought a T5 and a rear end without knowing much about either one have created that problem.
With 30 inch tires, a 3.73 rear end and the T5 you've described and assuming you shift at 2500 rpm, here is what your shift picture will be:
You will shift from first to second at 15 mph.
You will shift from second to third at 25 mph.
You will shift from third to fourth at 40 mph.
You will shift from fourth to fifth at 60 mph. At 65 mph (in fifth gear) you'll drop down to 2100 rpm (which is workable, although I'd be happier with slightly higher)
For the sake of comparison (and because some people for whatever reason don't seem to understand how I can make a T5 with .86 fifth work with a 235 and a 3.07 rear end), if you had a 3.08 rear end, a T5 with a .86 fifth gear, 26.5 inch tires and assuming you shift at 2500 rpm, here is the picture:
You will shift from first to second at 16 mph.
You will shift from second to third at 28 mph.
You will shift from third to fourth at 43 mph.
You will shift from fourth to fifth at 62 mph. At 65 mph (in fifth gear) you'll drop down to 2200 rpm (remember the .86 fifth ratio)
So, is there any difference between what I've got and the 3.73? Not much, as you can see. I drive a bit further before I shift but that's better for city traffic. Very minor difference overall and I really hope it helps folks understand better. In Dallas, we have several long streets with no stop signs or street lights and 40 to 45 mph speed limit. The shift from 3rd to 4th was set specifically for this. I shift to fourth at 43 mph (2500 rpm) and then I can drive along very easily, efficiently and with better economy.
Now for the sake of another point of view let's say you decide to use 28 inch tires and you have the T5 you described plus the 3.73 rear end. Let's see if 2 inches less in tire diameter changes the picture for you a lot or just a bit. Actually if I'm thinking right one factor will be improved...
You will shift from first to second at 14 mph.
You will shift from second to third at 24 mph.
You will shift from third to fourth at 38 mph.
You will shift from fourth to fifth at 56 mph. At 65 mph (in fifth gear) you'll drop down to 2200 rpm (same as me).
In my opinion 28 inch tires will be fine, they will cost you less and they will improve one thing. The shift from first to second and second to third will be almost indistinguishable from the 30 inch diameter option. Shifting to fifth at 56 mph is good and there is the improvement. You increased the cruising speed by 100 rpm. Which believe it or don't will make a difference. I'm fine at 2200 to 2500 rpm and unless I'm in headwinds or very hilly zones all will be Jake. You haven't said where in TN you live so it is not easy to hit the bullseye, but we ought to be able to get you close. Ideally you ought to only do the transmission/rear end/tire size calculation exercise once. Done correctly we should use only the first 4 gears in town and then fifth for the highway. If you're using 5th gear in town, something went very wrong in your calculations or you're about to get a speeding ticket. Hope this is helpful.
And for one more very important note not related to gearing: If you use taller tires on the rear and smaller tires on the front, make absolutely certain to have your caster angle adjusted correctly. Taller in the rear and shorter in the front by definition reduces your caster angle. That makes your truck steer easier but it may cause it to wander. If you fail to have at least 2 to 2.5 degrees of positive caster, even if the rest of your front end is in perfect shape, you'll have unstable steering. 3 degrees is best, but it will increase slightly the effort to steer in a parking lot. I add this because 30 inch tires may not work well for the front of your pickup. It was designed for 6.00 x 16 wheels/tires which are 28 inches tall and skinny by today's standards.
As for a rear end that fits nicely in the AD truck, one option is the 12 bolt rear (late 60s, early 70s) Chevy truck. 15 inch 6 bolt wheels are what it came with. You can even alter the stock 1950s parking brake cables to work with it. Good luck!
