I started out years ago towing our 7,000 lb trailer with my old chevy 2500 with the 350. I tow mostly in the Sierra and Rocky Mts. I hated the way I had to slow down to 45 mph going up the grades. So ...
Get a diesel and be done with it, no more issues. Towing only a 7,000 pound trailer I doubt you'll be slowing at all. I used to tow a 6,500 pound boat/trailer up some steep grades with my Ford F-250 with a 7.5L gas motor. Speeds were 40-45 mph. I then got a Duramax diesel and the same hills were taken at whatever the speed limit was, usually 60-65 mph and in cruise control. It was a night and day difference. I'll never tow again with a diesel.