FYI, this may sound counter-intuative, but adding your front gross axle weight rating + your rear gross axle weight rating, you bet a number er that is actually greater than your GVWR. Example: on my 22 2500, the GFAWR is 5500 and the GRAWR is 6390 which adds up to 11,890. But my GVWR is 10,000.
1490 is really not very much payload for towing a Travel trailer. My former GMC 1500 with 6.2L and 10 speed had a payload of 1650. By my calculations that was going to be marginal at best for our new travel trailer. That's even considering we travel relatively lite and only two people. Our trailer is a 30 footer that's 7034 empty and about 7600 loaded. Our tongue weight is 941 empty and 1008 loaded. We have a large front slide out a d also a front kitchen, but still that works out to a tongue weight of a out 13.2% which is right in the good zone.
Finally, a CAT scale is your best friend for answering these questions. It's quick, easy and cheap and until you get real weights from a scale, it's all guess work and speculation.
In the end I upgraded to a RAM 2500.