You really want swivel ends, not fixed crosstube ends.
Then it's a matter of drilling and tapping your steering box. This can be easy or difficult, depending on the steering box and skill level. I believe you have a Saginaw box, so this should be applicable: Pirate4x4.Com - Extreme Four Wheel Drive
While you are shopping surpluscenter.com, you need to get the right fittings and hoses for the ram and the steering box.
You should also add a decent power steering cooler if you don't already have one. Hydro assist creates more heat in the fluid, and the cooler will add extra capacity. You might have to look into a larger reservoir as well.
Lastly, I wouldn't even consider adding hydro assist if any of my knuckles, steering arms, tie rod ends, or tie rods weren't up to the extra pressure. Stock FJ40 stuff is small, IMHO, and probably won't live long with big tires and hydro. You'd probably want to upgrade your knuckle studs with ARP studs and maybe even consider a 5th stud mod or 6 shooter knuckles and arms, change out your tie rods and drag link to 1.5" DOM, and maybe even ditch the TRE's in favor of strong 3/4" heim joints (or switch to FJ80 ends) if your truck sees little street time. One of the hardest things to winch off the trail is a truck you can't steer properly.