I had a 12 Chevy 5.3 and it was rated 315HP. I believe the 14/15 5.3 is rated 340HP. I had a 2000 GMC 4.8 and I believe it was 270HP. My 12 chevy transmission did a lot of hunting pulling my Whitehawk 27DSRL so I upgraded. My 4.8 GMC was a great truck/engine. Never had a problem with it. I sold it with 186,000 miles on it. Ithink you'll be fine if your not having trouble with it now.
2015 Jayco 27DSRL
2016 Little Guy CIRRUS 800 Truck Camper
2015 GMC SLT 3500 Duramax Crew Cab, SRW