drum/drum prop. valve install, what to buy...? will it work?

[SWEET7T]

I did a search and came up with some info. But I still have questions...

My '70 came with a prop valve (or is it called a distributor valve, I hear that they are somewhat different ). I am blessed with the early locking rear, and I want it to stop. Would it be worth it to replace the factory valve, or buy an adjustable prop valve, or what?

Will an aftermarket valve just be plumbed inline with the rear brakes, or is there something that replaces the stock unit all together (is tied to both front and rear)?

If I do install one on the rear brake line, should I expect that I need to apply more pressure on the pedal to stop the truck (since I will cut pressure to the rear brakes but still have the same to the front)?!

Thanks everybody!!!