3.07 or 3.73 gear decision.....

[lukecp]

As stated in my earilier post, it looks like i am going to be in need of a new rear axle for my truck pretty soon.

So....i'm debating on putting in another 3.07 geared axle or swappiing to 3.73's. Either axle will be a used salvage yard unit.

Right now with my mild 350 and 3.07 gears i pull ~3,000 rpm at 75 mph, and usually get around 13 mpg on the highway, going around 65 mph with the engine pulling 2,500 rpm and lots of donwshifting/passing. With the 3.73's i will be pulling ~3,000 rpm at 65 mph. My mild cammed engine makes peak tourqe in the 2500-3000 rpm range.

Any guesses on how much the 3.73's will negatively affect my gas mileage?

I want 3.73's in the truck for my future plans, which are either an OD tranny, or putting a much bigger cam in my 350 and slowly turning the truck into a non daily driver hotrod. So i don't want to swap in anohter 3.07 geared rear only to swap it out for 3.73's six months or a year down the road.
I would go with 3.42's, but they never came in 5-lug coil spring axles, and getting my rear rebuilt is far out of my price range.

Any imput is greatly appreciated