I came back to this project after being away from it for a while and things suddenly clicked in my brain. The key is to remove the lift pump so that you can more easily access the vacuum pump screws. I had the pump out in less than 15 minutes.
Don't forget to order fresh gaskets for your vacuum pump and lift pump. You might also consider replacing your lift pump while you're in there, since it's easy with everything off.
Here's how to do it:
1. Remove bonnet by raising it to vertical and lifting it off the truck with the help of a friend.
2. Remove rubber engine cover, replacing oil filler cap once it's off.
3. Unplug oil temperature sensor plug from sensor. Unplug wire from fuel solenoid cut-of on injection pump. Move electrical harness out of the way.
4. Using a flat spanner wrench, remove engine fan. Remember that it has reverse thread, so turn clockwise to loosen.
5. Unbuckle air filter canister retainer straps. Move air canister up on top of the motor and out of the way so that the canister bracket is exposed.
6. Take a few photos of your injector pipes so you can see how they're arranged and which pipe plugs into which port on the injection pump. (or, don't, and then call
@DefendersNW asking for photos like I did)
7. Using wrenches to hold each side of the fitting, carefully loosen all fittings on injector pipes, then remove pipes and set aside in bucket so that you don't spill fuel everywhere.
8. Using wrenches (9/16", I believe, two required) to hold each side of the fitting, carefully loosen and remove fittings from fuel lift pump the side of the motor. Move the inlet and outlet pipes out of the way and arrange them so they're angling up and not spilling fuel everywhere.
9. Remove the hex cap screws (10mm head) that hold lift pump to block. Remove the lift pump and whatever gasket you can peel off easily.
10. You should now be able to access the vacuum pump.
11. Loosen hose clamp and remove vacuum hose from rear of pump. Move aside.
12. Working your way around the pump, loosen and remove all six hex cap screws (10mm head) holding the vacuum pump to the block. You will have to get creative here. These are not high-torque screws so I would use a 1/4" drive ratchet with a 10mm bit and a few short extensions where necessary. A 10mm box-end wrench is handy for reaching some of the ones on top. You might find it easier to reach some of the bottom screws from below the truck (make sure the transmission brake is on and the truck is chocked).
13. Remove the old vacuum pump and whatever gasket you can get off by hand.
14. Very carefully, with a flat scraper, scrape any remaining bits of gasket off the side of the block. It helps to have a sharp scraper if you've previously used gasket sealer here. Using a rag dampened with some brake parts cleaner, gently clean the mating surface of the block, along with the mating surface of your new vacuum pump.
15. At this point, you will need to turn the motor around using the 27mm hex cap on the bottom-most pulley on the front of the motor just under and to the right of the pulley where the engine fan attaches. Put the truck in neutral (make sure your transmission brake works, that you're on a flat surface, and that the truck is chocked) and using a long ratchet (preferably with a swivel head), turn the motor crank while you put your other hand on the crankshaft lobe that's exposed through the hole where your vacuum pump attaches. Keep turning until you feel that lobe rotate in. You'll know that it's rotated enough when you can easily place the new vacuum pump more or less cleanly against the block.
16. Fit new gasket to vacuum pump and reinstall. The by-the-book way is to use a gasket and nothing else, but I smeared some Right Stuff gasket maker lightly on my new gaskets here. I do this to keep them from leaking and to make installation a little easier, as the Right Stuff holds the gasket to the block. It's really not that hard to remove Right Stuff with a scraper, not much harder than shitty old paper gasket anyway. See workshop manual for torque specs. It's not much. Don't use more than a shorty 1/4" ratchet and gently at that.
17. Reconnect the vacuum line to the vacuum pump and tighten hose clamp.
18. Do the same for the lift pump. Gasket, then gently screw it back on to correct torque, then carefully reattach pipe fittings being extra careful to make sure that you haven't confused inlet and outlet. Look at the arrows on the lift pump. The inlet line should come from your bulkhead and the outlet line goes to your fuel filter.
19. Work backwards through the previous steps and carefully reconnect everything that you've removed. Be extra careful on the injector pipes and put a 15mm spanner against the flat portion of the injectors themselves to hold them in place as you tighten the fitting caps on the pipes. Be careful not to cut or break your injector spill return lines, either.
20. Remove the big ratchet you used to crank the motor and replace the engine fan, screwing counter-clockwise (remember, it's reverse-threaded).
21. Triple check your work. Also remove any rags, forgotten tools, or loose fasteners.
22. Open the bleed screw on your fuel filter housing slightly. If you have an aftermarket inline 12V fuel pump installed (you know you want one!), simply turn it on to bleed the fuel system. Otherwise, temporarily unplug fuel cut-off solenoid wire and crank motor until fuel is sputtering out the bleed screw you opened and there are no bubbles. Re-tighten bleed screw.
23. Reconnect cut-off solenoid wire if you unplugged it and start motor. Observe pipes and pumps for any leaks. I did a road test with the bonnet off so that I could see any major leaks while the truck was under load.
23. Replace bonnet.