As NC Hauler suggested, the best thing to do is spend $10 and get weighed. You can then use a calculator such as this for finding what is left over and getting a feel for how much fifth wheel or TT you can tow:
http://www.towingplanner.com/Calculators/TowingScaledWeightsWithout weighing, you can estimate your weights and work backwards from you "tire and loading information sticker" on your doorjamb by using this calculator:
http://www.towingplanner.com/Calculators/TowingPayloadEstimateFor estimating PIN weights to stay within your ratings, you can usually use the percentage of pin weight for the dry weights and then apply that either to an estimate for your actual loaded weight or to the camper's GVWR. And, of course- I've got a handy estimator for that too. :):
http://www.towingplanner.com/Estimators/TonguePinWeightFromDryOnce you know some weights, you can narrow in on campers that fall in those ranges.