Anything over 33" would be terrible on 3.73's.
Ran 33/35's on 4.10s, and 39's on 4.56's and it felt good.

I wouldn't want anything less than a 3.73 behind a 5.3 if I had any intention of towing anything over 3500lbs. The max tow package has 4.10's. If I was going to run a 35" tire or bigger I would want the 4.10s.

On a 2012 the 6 speed auto helps out a bunch compared to the old 4 speed. My 14' has 3.42's and more power. It tows like a dream considering the gear it has. The 3.23 trucks are turds though. The towing capacity drops like 2500-3000lbs from the 3.42.

my old 01 silverado with the 5.3 has 3.73 gears and i put 285/70/17 10ply tires on it. I can def tell a difference on the highway lol. It's not bad though.
still pulls a 31ft camper with a large popout just fine

My mega cab runs 3.42's on 37's They are actually about perfect for a daily to be honest. That said, I also rarely hook it to anything anymore. It get's a little boggy when we hook up the camper to it. That also has to do with a big single, too much fuel, and a few other things.

The last lifted gas job I built was a 76 power wagon on 44's that we ran a 5.56. That combo felt really good behind a ~400hp small block.

To be more on topic. With the new 6 speed GM is using, 35's would be fine with 3.73's so long as you are not planning to haul heavy with it regularly. If OP is going to be hauling that enclosed trailer I would probably opt for 4.10's with the bigger tire.