S10 and C10-gears interchangeable?

[Slonaker]

An acquaintance from another, unrelated, board asked me the following question. I didn't know the answer, so I offered to post his question here. I'll send him a link to the thread...

I have a 1985 Chevy 1/2 ton 2-wheel drive pickup with a 2.73 10-bolt rear end. I'd like to swap it out to a 3.42 since I really only use the truck these days to haul stuff and it could use some help getting started on an incline with a load.

I also have a 1989 S-10 Blazer 4x4 rear axle under my 1953 Chevy 210 with 3.42 gears in it. I'd like to swap in 2.73s to bring my highway RPMs down and maybe get better mileage.

I know the rear ends themselves will not swap, and I wouldn't want to, but can I swap the gears between the two rear ends? Are they the same, or at least interchangeable?

Thanks for helping him out.

Slonaker