i've got a '95 gmc 2500 2wd pickup towing a fifth wheel. truck hauls it very well but sags a bit in the rear. thinking of investing in an airbag set up. any opinions out there would be greatly appreciated......
As long as your trailer rides reasonably level there is no concern. If it does not, check your trailer pin weight vs the truck's rear axle capacity (GAWR) - you may be overweight. When loaded a fifth wheel is pretty heavy on the hitch and often far more than the advertised pin weight. 20% of total weight is fairly typical.
Air assist, e.g. the Firestone Ride-rite air spring system, doesn't acually increase GAWR and GVWR, but it can be used for leveling. See http://www.ride-rite.com/
Goodyear make sthem too - http://www.goodyearindustrialproducts.com/airsprings/about.html