I just bought a front disc conversion kit from SSBC (have drums in the rear).

My question is how do you adjust the proportioning valve? I know the front discs should have pressure between 1200-1400 psi, but what is the bench mark for the rear drums.

Any help would be appreciated.  

I would talk with a rep from SSBC. The proportioning valve reduces pressure to the rear drums because they will lock up before the front discs. I adjust mine by doing hard stops and adjusting after each stop until front and back brake equally.