The most accurate way to determine your available pin wieght is to go get your truck wieghed at a CAT scale while it is full of fuel and other stuff including passengers you will have while pulling. Then calculate 2 things:
- Max pin wieght based off of GVWR which is GVWR minus actual truck total wieght. This is the max pin wieght you can have an maintain all of your manufactures ratings which really means warrenty
- Max pin wieght based off axle rating by RAWR minus actual rear axle wieght. This is the maximum allowed remaining payload (meaning pin wieght) that you can legally have on the road (number of trips and distance doesn't matter). Axle and tire ratings are DOT legal requirements while vehicle GVWR is not.
I suspect the pin wieghts you are talking about in your post are the manufactures brochure/advertised pin wieght is dry trailer pin wieght, doesn't mean much unless you really are going to tow it totally empty. Typical pin wieght of FWs is about 20% of its loaded wieght. So take the 2 numbers you calculated above and multiple them by 5 to get the approximate FW GVWR you can tow. Use the number calculated by GVWR for maintaining manufacturers ratings. Use the number calculated by axle wieghts for the maximum you can legally hook to your truck on public roads
With a gas powered 3/4 ton rig I normally suggest you stay below 10k GVWR FW but since you are only towing very occasionally you can probably legally tow around 12k# GVWR FW and just put up with the poor power performance for those few times.
