2001 dodge 3500 2wd looking for best mpg towing

Hey guys just bought a 01 3500 6sp with 3.55 gear im hauling my pulling truck with it on a 24ft trailer looking for whats the best way to go on getting the best mpg out of it not wonting to make big power just towing with it thanks in advance for the help

Are you wanting just a box or how far into it are you wanting to go?

Yea a box and maybe some injectors I'm not wonting to do a turbo just keep it cheap as I can and easy