Do you already have the D60, or do you need to source one first? IMHO if you plan on keeping the truck for a while it may be a wise decision to spend some money now and not have to ever worry about axle failures in the future. With the D60 you also get larger brakes, which is always a plus - factory halfton brakes with 37s is gonna be slow to stop.
Also, remember larger tires and low gears are an excellent axle shaft breaker combo. So if you were keeping the tires closer to factory then the 10-bolt should work alright, but with the biggies IMHO you're setting yourself up for trouble down the road. Having spare parts is excellent, but what if the carnage happens when you do not have them (or the tools needed to swap them) on board? Our "expo" truck has 1-ton axles and still runs 235 tires, may not be the best for ground clearance but it's a size widely available everywhere at any give time and more importantly does not stress the axle shafts when truck is loaded (or is working hard to help recover a fellow traveler), thus minimizing the chance of something going kaboom while we're in the middle of nowhere.
Here's a thought, didn't the 3/4-tons have a D44HD front axle? In Ford applications the 44HD got the same brakes as the 50 and 60 so that takes care of stopping the truck once the big tires are on, and they also seem to hold up well to responsible driving even with larger tires. It's been a while since we've messed with a non-customized GM product, does the same situation apply for them as well? If yes then you could run the 3/4-ton axle instead of the D60, it's bound to be cheaper and easier to locate and will thus give you both an upgrade in strength and braking ability and a break in your budget to use towards other projects. A happy medium of sorts...
