Jody, just curious why you think the 3/4 ton axle is less safe than the 1/2 ton. The 3/4 ton has larger brakes, which I always viewed as a safety advantage.
Others can correct me, but I'm pretty sure that your AD 3600 would have a split driveline with a torque tube on the front to the carrier bearing and an open driveshaft to the back connecting to the Eaton HO52 rear end.
That is good news when it comes to changing rear ends. You won't have to mess with the torque tube. You would want a 1955.1 or later 3100 rear end because it is would be set up for an open driveshaft. 1954 and earlier 3100's had a torque tube. You might also find that any year 3200 might fit (guessing here) because the two piece drive line probably had a torque tube on the front and an open driveshaft on the rear similar to your 3600.
Installation should be fairly easy and your existing rear driveshaft might even work. The ujoints might be a different size in the in the 1/2 ton rear end than what fit on your original Eaton, but if so you should be able to find 'combo' ujoints that match to your original driveshaft and your new rear end. You just need to get the stock specs off of both and order a ujoint that has one side that fits the driveshaft and one side that fits the differential.
If the 1/2 ton rear end that you have is set up for a torque tube, it will be a big project to convert and install it.
Send me a PM if you need a 1/2 ton rear end set up for an open driveshaft.
Matt
