Drum Brakes Sticking

Have you rebuilt or replaced the wheel cylinders? If not, then that could well be the source of the problem. For a car that old, not rebuilding or replacing all the wheel cylinders is asking for trouble.

And be aware that the spring shave to be right and matched. You may have flipped some of the springs; they have to be exactly right.

Also check the new shoes; there is a primary and secondary on each side and the primary has to be the front one; if you reverse them, then you will get the drum grabbing.
Does this car have drums or discs up front?

You post may be a bit confused on one count: there is only one rubber line to the rear and that feeds both rear drums. And, if your uncle clamps any more old rubber lines, he needs to just go out and but replacements. Clamp[gin old rubber lines is a great way to finish them off in a way that locks brakes on.