A couple days ago I, for the first time, sheared off a wheel stud while out wheeling. I wasn't able to find a lot of solid information about replacing them on here, so I thought I would post my results.
I saw mentioned in a few threads that people had to remove brake components, or even pull the whole axle to be able to get at the studs. I also saw mention in a few places that Dorman studs would not fit quite right, and that factory studs were the only way to go.

I can only speak for the rear wheels on my 91 PU 4x4, but I have good news.

1. I was able to remove the old studs, and reinsert the new studs by jacking the problem wheel, and removing the wheel and brake drum. I then rotated the hub so that the stud i wanted to remove had enough room behind it in relation to the brake components. Driverside, this put the offending stud at about 2 o'clock. One good smack (about 75% power) with a 3lb sledge broke it loose, and a couple gentle taps pushed it through the back without launching it into the brakes or hitting anything else.
2. Dorman studs ($2 ea) went in without problems, saving me from buying Toyota studs ($8 ea) which were just about identical upon inspecting some at the dealer.
3. To install the new studs, I bought a $3 'acorn' style non-capped lugnut with the correct threads, that I will save as my stud-installer. I applied a very light coat of silver anti-seize to the serrations of the stud, and poked it in through the back of the hub. I then put a couple washers onto the stud (making sure the washers would fit over the shoulder of the studs, not just the threads) then installed the acorn nut flat side on first. Using a 3/8" drive ratchet and socket I slowly tightened down the acorn, pulling the stud into place without any problems.

So, let there be no confusion about rear wheel studs on 91 PU 4x4s.

And for reference, the Dorman part# of the studs I used, which match the factory studs, is 610-312.
For further reference, Dorman parts: 610-312.1 / 98520 / 98520.1 are identical to 610-312, just packaged differently. Handy to know if the base #'ed part is not available.