Is your master cylinder for a disc/drum or disc/disc car? I remember something about a restrictor that you remove for a disc brake car, but you leave it in for drum brakes.

Are you sure that you have the rear brakes plumbed to the correct side of the master cylinder? I was thinking that the rear of the master cylinder was the rear brakes, I plummed mine up that way and had to redo it.

Can you just move the brake rod hole on the arm tio change your ratio? I think that I drilled a hole something like 3/4" closer to the pivot point to change my ration to 6 to 1.