I think the military Blazers used 10-bolts just like the civilians.
For the semifloating 14 bolt, this would give a significant strength increase but would also require some work to keep the 6 lug pattern. The 8 lug, semifloating 14's were pretty common in 3/4 ton pickkups and Subs up to '87 and are pretty much a bolt in deal. These can be converted to 6 lugs by either new axle shafts and brake drums or redrilling these parts (I got an estimate of under $100 for an axle shop to do this). The factory 6 lug versions, to the best of my knowledge, were only available on the "newer" style trucks with independent front suspension ('88 and newer pickups, '92 and newer Blazers,Tahoes, etc.) and would require the spring pads to be moved in order to install in your Blazer.
I'm a firm believer that a 10-bolt can be beefed up enough to handle moderate tire sizes and use. The first upgrade is the 30 spline axle shafts that became available in the '89-'91 model years. The next step up is to replace the factory carrier (aka differential) with a full case unit like a Detroit Locker, TruTrac, etc.. I would not recommend using something like the EZ locker or Lockrite because they do not do anything to strengthen the weak factory carrier. I've used a rear 10-bolt in my '90 with alloy 30 spline axles, Detroit Tru-Trac, and aftermarket 4.10 gears, for about 1.5 years with 33" tires and the last year with 35" tires and do pretty serious trail riding about once per month with no issues out of the rearend. I have broken a couple of front axle u-joints, body mounts, and spring shackle bolts to give you an idea of how it's used......though I am planning on upgrading the front and rear axles in anticipation for bigger tires and harder use. With the above mentioned mods, i think you would be okay for 33"-35" tires and easy to moderate use with the 10-bolt, but it really depends on how hard you drive it.