I pulled 5K lbs. (26 Maxum CC) with my '89 S-10 Blazer; ONCE, and once only! It was only about a mile. I would have to estimate you do not want to pull more than 3K lbs. TOTAL. Subtract gear, trailer, and fuel, and you are back to about 2200 pounds for the boat dry.
Like we always say here on the board, "Yeah you can PULL it, but can you control it and STOP it?"
I would say go with at least an after 1996 model year 4.3L. (They went to Vortec that year, and got a little stronger.) Also, tranny cooler, and go for 4 Door, 4WD, and the tallest gear ratio you can get. Check the codes printed on the card in the glovebox for the gear ratios. (GT4 should be 3.93 gears. GT5 should be 4.10.)