1980's typical GCWR for a 454 is 14500 for 3.73, 16K for 4.10 and 19K for a 4.56. Later years when the vortec version hit the streets about 95 or so, then the warranty ratings went up 500-1000 lbs or so. Why do I say warranty ratings.....well, it is just that, a warranty rating where if over this amount, GM, For etal can deny you warranty work done. As noted, there is no legal standing from ANY state, federal level as to you have to follow this amount.
Where you will have to be, is as you note, your toad does have brakes that function. WHich is good, some states require ANY "towed" item to have brakes over 1500 to as much as 4500 lbs. Wa st where I am, it is 1500-4500 or 40% of the tow rig gvwr. I personally would not recomend towing a trailer that puts you much over about 1000 lbs of gvwr, then after this, you do notice a serious lack of braking power, even if legal per say.
Have fun with the setup.
marty
