Flares, front or rear only fit the special ZR2 body parts. On the front you'll need to put ZR2 fenders with the special lip on the Blazer. On the rear if you know a good body guy he might be able to mod your rear wheel wells by adding the flat lip needed. But as mentioned rear truck and 2 door Blazers are shaped differently.
There are also small Flarettes that bolt to the front bumper and valance so the front flares don't just end in mid air abruptly.
There's a guy here locally trying to sell just the 4 flares, one is in 2 pieces, on Craigslist for $50. Been on there over a month.