would 373s work for this?

[bigscooter]

hi guys, i can't stand this low geared rear end any longer(456s probably). it's a '91 r3500? 2wd crew cab. it is a small block, the tranny is the manual with the low and 3 speed. my rear end is not dually. I'm hoping 373 gears won't be too high. i value economy more than strong hill climbing. i don't tow more than 5k (usually just motorcycles and VWs around town). i do dream of some day installing a 5-speed. Am i barking up the wrong tree?

Thanks!