I'm not an expert on the blazers... but:
The blazer is not rated for heavy towing. About the only thing that you can tow that is withen the weight rating of the vehicle is a M416 1/4 ton trailer (it does not have service brakes, just parking brakes). That said, I know that a blazer will also tow a M101 3/4 ton trailer without problems. The M101 and M101A1 don't have service brakes, the newer M101A2 and M101A3 do have surge brakes (M101A2 has the CUCV rims so that would be a good one for you to get...). Surge brakes have a piston (in the brake master cylinder) that is activated by the trailer "pushing" on the tongue (aka pushing on the towing vehicle) when the towing vehicle slows so you don't have air lines to the vehicle.
The heavier and/or larger trailers (such as the M332) have service brakes that are air over hydraulic (for the "smaller" single axle ones) that are activated by air pressure from the truck pusing the piston in the master cylinder on the trailer. The brakes are applied when you apply the brakes in the towing vehicle (since the brake systems are connected). Some of the even larger trailers have full air brakes where the air actually pushes the piston that moves the brake shoes in the hubs, but all you really need to know about them is that they also have the air lines to the towing vehicle just like the ones with air over hydraulic setups...
So, to be honest, you really only want to tow trailers that don't have the air lines on them with a Blazer so that you won't exceed the truck's towing capacity (braking/control capacity in addition to the lower rated rear end components...).
Good luck.
