This is a week old but I haven't been able to reg for a few days so I thought I'd still try and share some info.
There are standard GM 6-lug pattern (6x5.5") 16.5" wheels available. It was never a factory option but plenty of aftermarket wheels are available. I know Summit Racing has some.
You can fit the HMMWV tires under these trucks but I wouldn't do it under a Blazer without the previously mentioned upgrade to larger axles and deeper gears. The 3.08 gears alone would scare me off.
The military has been putting HMMWV tires under the 1-tons for quite a while. Since at least someone figured out that 36's + 4.56 gears = 70mph capability. I know a guy that was a vehicle mechanic in the Army in the early 90's and he remembers doing it during Desert Storm.
Mine will go along just fine in the slow lane of the highway with the big tires. I remember when I was in the Marines and driving them on 31" tires they sounded ready to explode at anywhere near 55.
As far as fitment they rub a bit on the fender edges up front. In the rear you'd have to flex the wee outta the rear suspension to make them rub, Chevy's are famous for that. Trimming back the front fenders on each lower edge helps some but they will still rub. Part of the problem is that the front axle/suspension on 73-87 GM trucks is not actually centered in the front wheel wells...it's an inch or so towards the rear of the vehicle from center. Moving the axle so that it is centered goes a long way to eliminating rubbing. This is why some guys have 6" of lift and 35's and still get rubbing. Some people move the axle forwards by redrilling the center pin holes in the front suspension while others use
www.OffRoadDesign.com's 1" zero rate add-a-leaves to get 1" of lift and space the axle forward either 1" or 1.5". I plan on using the Zero rate and some 2-3" lift springs in the long term but for now I'm going to put some 4" lift springs on that a friend of mine has. It drives along fine right now but if I go wheeling I'm afraid I might damage the tires or fenders a good bit by flexing the fronts into the fenders.
Oh, and to best do this you must get some stock GM 16.5" wheels of the era. They're a bit narrow but the tires fit fine and the bias plies (having a round cross section instead of flat like radials) couldn't care anyways. I needed one of these wheels for my spare and was GIVEN one by a guy that had it sitting in his garage.
LASTLY...consider a frame brace for the steering box if you're going to run big tires. ORD above makes a nice one. Hell, I put it on every one of these older GM's even if it has stock tires.
