7500 pounds dry if too much for most half tons, that truck included. Add 1000-1500 pounds for the typical RVing family.
If the RV has a 7500 pounds GVWR, then it might be good. I recommend under 6000 pounds dry for the most capable half tons. Usually some other rating is exceeded if towing an RV at the tow rating. Receiver, payload, rear axle are likely to be exceeded for a 9500-ish pound RV. Most 9500 pound boats would be fine. :)
3.42 axle is fine with the 6-spd trans. It provides better overall gearing than an old 4-spd with 4.56 gears. GM does not offer a 3.73 axle with the 5.3L. IF you really want a new GM half ton, I highly recommend the 6.2L/NHT package. A lot more power, a little more payload. Anything wrong with your current 3/4 ton?