So I finished replacing my alternator. I am going to get my original Hitachi alternator rebuilt and have it on-hand, since consensus seems anything but a new or rebuilt Hitachi alternator is unlikely to last long. But because I didn't want to be down for that time (little did I know the lower alternator bolt would break and leave me down for a week anyway), I got a junkyard alternator. Unfortunately I wasn't able to get a Hitachi one from the junkard. It was a 13900 built in Malaysia. It was a greasy mess, so cleaned it with a can of CRC Lectromotive electric parts cleaner, which worked great, and got it tested at Autozone.
It turned out I couldn't see well from the top, so I was wrong about not being able to get my arm between the battery tray and the power steering pump. I'm 5'6" and medium build with fairly large forearms, and I could do it with a fair amount of struggle. If you were significantly bigger, especially in the forearms, you might not be able to do this.
Any specs quoted below are from memory, so I recommend verifying in the FSM before doing this. Here are my steps -
Remove the plastic windscreen on the underbody
From right behind the steering rack, reach up and remove the alternator ground screw
Use a flat blade screwdriver to push the plastic latch on the wiring harness off the metal bracket attached to the alternator
Put a magnetic finder on the alternator mounting nut (to prevent it from getting lost, you don't want to lose this in the power steering rack)
Loosen the nut on the front of the idle pulley FIRST!
Release the belt tension by unscrewing the bolt on the bottom SECOND! - Otherwise you'll screw up the tensioner mechanism
Work the belt off
Remove the battery and plastic tray
Optionally you can loosen the alternator top bolt, and remove the bottom bolt to possibly gain a half inch for doing the 2 steps below. I was able to barely do it without loosening the alternator.
From the top, remove the voltage regulator plug (release button faces the firewall)
From the top, remove the positive lead by pushing the rubber boot out of the way and removing the nut
Here is where my truck will deviate a little bit (I have an electric radiator fan) - remove the radiator fan and shroud
Break both alternator mounting bolts loose
Unscrew and remove the top bolt from above
Find its nut with the ear below your engine
Remove the bottom bolt from below
There is no good way to describe how to jigsaw the alternator out of position, but you basically have to move it a little to the passenger side, and bring it forward in front of the radiator. It will take some wiggling and muscle to release the alternator top mount from the engine bosses. Be a little careful, in the manual transmission, the oil level sensor's plastic socket is right below the alternator.
Carefully bring the alternator across the radiator to the driver's side, and then Tetris it out between the radiator and anti-sway bar. There is an inch more room here that makes the difference
After the 2nd replacement, I decided not to reattach the metal wire harness bracket to the new alternator. The wiring harness seems much stiff enough to support itself.
Work the new alternator back into position the same way the old one was removed
DO NOT USE lubricant on any bolt threads or nuts. Wash them off with parts cleaner if necessary. You may want to replace the lower alternator bolt if it looks corroded. The head of mine broke off when tightening it. I believe it is a M8 1.25 20mm flanged head bolt. I used a class 10.8 I found at Autozone.
Put the top bolt in first
Optionally put in the lower bolt, but you could wait until after you wire the positive lead and you might gain half an inch of clearance for the positive lead and voltage regulator plug
Get someone to spin the top bolt for you while you get underneath the car and start the top nut onto the threads, and get the ear seated against the alternator mounting arm
From the top, reattach the positive lead FIRST! If you try to do the ground first, you'll be unable to correctly seat the positive terminal between the two nuts on the positive stud of the alternator without cracking the plastic insulator. Someone did this to the junkyard alternator I had. So I swapped the insulators with my old one.
From the top, reattach the voltage regulator plug
Reattach the negative lead from the bottom
Tighten the alternator top bolt (60 NM)
Tighten the alternator lower bolt (30 NM)
Put the belt back on
Finger tighten the idler pulley nut and back it off a quarter turn
Tighten the tensioner belt (I have another thread with guidelines for this. The short version is hand tighten with an extension and no wrench, then use a wrench 2 full turns for a new belt, and 1.5 turns for an old but good belt)
Tighten the idler pulley nut (25 NM)
Reinstall the radiator fan and shroud
Reinstall the battery plastic tray and battery
Reinstall underbody windscreen