Morning Bam!! What are the "slave units?" I'm putting back in the garage tonight and jacking it up. Also, do you know what size and thread the bolts were to get the drums off?Since yer talking about the fuel line...it's under pressure from the fuel pump...about 40+ lbs? You could try it with hose vs lines...but you'll need to be careful about any leaks or failures.
If the rear brakes are frozen...it's probably the slave units. I think the drums themselves should be good but it wouldn't hurt to have them checked. Do you know if the shoes are contaminated?
I would make out a list of all the things that the truck needs to be done to it. See how much yer parts costs are and see if it will be economical fer you to repair the truck. If yer not that experienced with the work, then you'll have to add in the labor cost of a shop to do the work. If it looks like it's gonna be too expensive, cut yer losses now and move on...unless you just want to make this a project vehicle...then it's how long yer gonna pump money into it. If it's meant to be a daily driver...you'll need to make some choices.