[Aces'n'8s]

I can't seem to find one at a parts store.

And you probably won't.

You need to search Jeff's Bronco Graveyard, AutoKrafter's, LMC, or even Ebay. Or you could try calling a local salvage yard for a used one.

 

[Aces'n'8s]

Well in that case could I use the valve from my truck? It has disc drum.

I don't know how the factory settings Chevy prescribed for its truck would function on your new axles. But, you could always try.

Or you could run a complete new rear brake circuit from the master cylinder. In this new circuit, you could install a "tunable" prop. valve. Summit carries a manual proportioning valve for about half the cost, or cheaper, of a new prop. valve for the older Fords.

But you will need to have some experience with bending and flaring tube. Also, you will need to rent/buy a double flaring setup.

Summit prop valve