Pittman arm question

[70's luvr]

I installed a 1980 3/4 front end on my 1970 C20 (For disc brakes) with the old front end, truck went straight down road. With new front end it does the same but the pitman arm is clocked at around 1 in stead of 12(straight up). The way the splines are on the box this is the only choice I have. I am using the 70 pittman arm. How do you get it centered? You can't adjust the center link so not sure what to do next.

Troy