Axle Swap For Gear Ratio

[86 Silver]

Ok fellas, here's my plan. I have an '86 K10 with new 350 (290hp) and 700R4 tranny. Currently I run 33" tires on 15" rims with a 2.5" suspension lift. My gear ratio is 3.42. WHen i run down the highway its constantly shifting to accomodate for the slightest of inclines...i hate that. really sucks down the gas when its always shifting down. Take it out of OD and it doesnt shift, but sucks down the gas....i know...ignore the gas guzzling 350 comments. :-)

I want to steal axles out of a Sierra Classic 2500 (Camper Special) with 4.10 gears and lockouts. It'd be a dierct swap I'm sure, but are the 4.10's too much or should I be looking for 3.73's? I am thinking this will actually help with fuel economy and not having to shift so much...or am i dreaming the impossible dream?

I will be putting in a 4" lift with 35" tires so that is the reason for my swap thought, or if i kept it where it sits, I know a 3.73 would most likely be perfect.

Thougths?