Easiest solution is swapping 4.10 gears into the original axle, once you find the used gear set or third member. We have a tech tip for that.
https://www.stovebolt.com/techtips/axles/1%20Ton%20Upgrade/This gets you comfortably to 55-65 depending on health of brakes, engine, and tire diameter.
For swapping axles the GM 14 bolt from a Cab and Chassis truck is about perfect swap for the AD 1 tons both single and dual wheels.
These axles are same width as the original, did have dual wheels and will again accept dual wheels in the AD truck, or single wheels if you like. Ratios available to about 3.31 too fast, 3.54 which may also be too fast.
Or the more useful 4.10 or 3.73, and other slower ones.
I agree that the T5 is probably a little small for the 1 ton.
The reasonable OD transmission choice is the NV4500 and you can find adapters and or info on adapting one, probably more work and particularly expense than changing gears or even entire rear axle.
Grigg
