73-87 gsimfab rear watts link kit help

[GRSEMONKY]

Has anyone installed this kit on a long bed, i have a 74 frame that I'm installing this on and it does not have the 3 alignment holes mentioned in the instructions. I tried reaching out to GSI and they couldn't give me any measurement. Just trying to figure out where i need to place the frame notches and bridge as the on hole that I thought was for the alignment is too far forward. If I bolt the air bag to the bridge it sits right on to of the cut out for the rear end so i need to figure out how far back to set this up.