Is Re-Gearing an option?

Ok here it goes:
I used to run 33's on my 2000 dodge ram 2500 4X4 extended cab, Automatic with shift kit and billet torque converter housing /4" exhaust no cat, no muff-K&N air filter, 65HP injectors, 1/2 banks 1/2 stock turbo with banks big head waste gate, Hypertech re-programer, flexilite electric fan, fuel boss mech lift pump. The truck is raised about 6"
I think it has 3:85 gearing.

My question is:
Im running 35" tires on 20" rims, I used to run 33" on 16" rims and I was "no BS" getting 24 MPG consistently doing 65 on my way to San Diego to Yuma (no I don't use the vehicles computer for figuring the MPG's, I do the math) My fuel consumption has drastically gone up for regular driving/freeway driving, and when I tow my 23' toy hauler my truck is bogged down(even when empty).

I wanted to go up to 37" on 16" rims but I don't want the fuel economy to really suck. If I re-gear the truck will I regain my MPG's and towing ability and still be able to run big tires (35" plus) or do I have to go back down to 33"s to have a good truck again?????

Thanks Guys-Hope this is enough info