Looking at going to some 31" tires and a RC lift kit, and seriously thinking of going from the stock 3.42 gears to 4.10 so my question would be looking for the most practical way to execute the ratio change. Would a ring and pinion set front and rear be the best bet?

I looked junkyards for 4x4s with GT5 codes in the glove box but they are pretty much non existent. Plenty of 3.42s and 3.73s but no 4.10s to be found.

I am assuming my stock rear end is the 7 5/8" and the front carrier is the 8.25? I will get underneath and look on the axle for the numbers and get a pic to make sure what it is.

Since installing the RC kit has both ends of the vehicle torn down enough to make getting to the differential cases a lot easier I'm thinking it would be the best time to try and switch over the gears.

One reason for the gear change is that with 235/75s and 3.42s it is mostly a slug on the road, engine rpm is only 2200 at 76mph and it is just sluggish most of the time. With 31" tires and 4.10 axles, engine rpm at 76mph would be 2365 which is a very appreciable difference. I have an Astro van with 3.42s and 215/65s that are 26" tall and it turns 2350 at 76mph, and it runs great on the open road. Plenty of torque, negotiates hills and passing other vehicles much better than this stock 99 Blazer with 235/75s.

What do y'all think?