I studied the hydroboost options for a while before pulling the trigger (95 F350). F-Superduty trucks don't show up in wrecking yards here. I got the Ford/Motorcraft booster from rockauto. Remans did not come with the intermediate pushrod. New lines too. Simply tee'd the return lines together at the ps pump. Moved the pin on the pedal up the 3/4-1" or so to prevent it binding.
EDIT: RABS valve was still in there. I don't believe it did anything before or after hydroboost.
What did it wind up costing you?
This is basically what I did as well. To be honest, I was lucky enough to already have the 2nd return port on my steering pump, and I still haven't done anything with the brake pedal yet. I got a hydroboost pedal from Wes but I'm waiting until I do bushings on the whole lot all at once.
I don't remember what the hydrobooster costs on Rockauto but if you just slot the bolt holes in the master cylinder so it fits you're only looking at another $30-40 for the PS lines. I think the booster was around $180 but I don't remember for sure.
As far as the RABS goes, I'd personally hold off until you start ripping your other brake lines apart. You may find it much easier to just run a new line straight from the Master cylinder to the rear axle, but that depends on what all you end up doing with the rest of the lines.
If you so choose, I can borrow a very nice flaring tool from a friend and we could bang out all new lines from the nice copper-nickel line some weekend. If you want, you know how to get ahold of me.