To be honest... maybe my dottage is beginning. And maybe part of it is that I deal with southern cars for the last few decades.
But I'd prefer swapping a complete ready to go rear end assembly and just bleeding brakes to having to crack open the pumpkin and deal with that gear oil and hassles of gear changes anymore.
Say I'll use a 60 rear end... if I want to swap gears, then buy another 60 rear end with different ratio and fresh brakes pop that sucker in on an afternoon. Sell the original.
I'd bet if you compared the cost, buying new gears, paying a shop to set them up (or wasting a ton of time doing it) and having to open the differential, labor to install the new swap, the nastiness. Then look at what you'd lose buying a fresh unit then selling your used one with different gearing (unless it is way radical.)
Yep, pay the cash for shiny new parts and no gear oil