IMO......it's more beneficial to swap in a junkyard axle w/ 4.10's. And you might even be upgrading to an 8.8 if you have a 7.5 right now. Might even be getting limited slip too.
I got a rear 8.8ls w/ 4.10's w/ 50k on the clock for $150. And a front d35 w/ 4.10's for $100 w/ 30k on the clock.
Look at it this way.....$400-500 for new to you axles that you can do yourself VS. $1000 for re-gear that most can't do themselves.
'01 XLT disguised as a '03 Fx4 Level II
Big. Loud. Slow. Bright.