You are far better off using the stock 87-93 mustang pulleys and brackets than trying to piece something together. There are plenty around in JY, mesages boards, and CL.
There aren't any compatible a/c pulleys, but I believe the v6 mustang power steering pulley can be used. It's larger and can offset an under drive crank pulley. I also believe it's used in road racing applications.
However, if replacing your underdrives, only the crank, water pump and alt get replaced.
Other 5.0s have compatible pulleys, but the sizes are mismatched. The Lincoln mark 7 has a huge crank pulley
You are far better off using the stock 87-93 mustang pulleys and brackets than trying to piece something together. There are plenty around in JY, mesages boards, and CL.
I want the stock pulleys. I am trying to get rid of the underdrive set that is on my car. It's not all that easy. None of the junkyards around here have them and CL is a crapshoot.