I tweaked the rear end geometry and brackets so many times I lost count. After debating over and over and factoring in excellent advise from successful racers like Ron a Sutton and my dad I ended up settling for two different anti-squat configurations. One for road race and a second setup for drag. I'm not 100% sold on arch slotted brackets so I went with multiple holes. The pan hard bar will be slotted as the load is perpendicular to the slot.
Here's some of the brackets off the CNC mill.
Here's the round stock and bushings my dad turned in the lathe to be able to setup the rear end. We bolted the 3rd member into the housings with shims the same thickness as the thinner gasket to locate the bar which we used for reference with the dial indicator to check the housing ends before I welded them on. We reused the old ends and turned them down to make a step in the tube side to locate them on center. I took most of the pictures with my dad's phone. This is all I have at the moment.
Here's the spacers that go between the brackets and the heim ends. I used 5/8" heim joints with a 3/4" shank and turned and cut left and right hand threads in 1" .156 wall 1022 DOM tubing I picked up from Morrisons shop.
I set the wheel base to 108". 2 deg pinion angle with the holes in the outside brackets at 90 deg (vertical/plum) and the bottoms of the inner brackets at 0 deg (level)
Here's the finished width. I was barely able to squeeze the 11.5" wheels with 315's in there. The rear end articulates well with a rolled edge on the inside lip of the fender.