I believe this is what you are looking at. You will have to make a plate liek this one
This is a pic and info given to me from GMC Pauls
Take a piece of steel 1/8" thick, 1 1/2" wide and 7 1/2" long, drill a 1/2"diameter hole centered on width of steel 1 1/2" in from the end, this hole you will use to install plate using the rear hole in block, measuring from the same end you made first measurement from mark the steel in center of width at 6 3/8" and drill another 1/2" diam. hole, install a pivot ball stud designed to screw into block in this hole and fasten in place using a lock washer and 1/2" nut. Slide the z-bar over the pivot ball stud on plate you made and lower the z-bar & plate into place installing a 1/2" diameter bolt with lock washer into rear hole on block and tighten once you have aligned z-bar straight with the frame.
And this is what I installed in mine
I bolted the hole on the right hand side, into the hole back near the bellhousing and welded the pivot ball in the blue circled hole
Hope this helps.