Fabricated A-Body spindle ideas and discussion

Upper arm geometry is okay, IMO. The anti-dive does create some dynamic caster change that isn't always great, but is tolerable. Hotchkis eliminated the anti-dive in their A body upper arms.

Ackerman is the triangle from the lower ball joint, through the outer tire rod end, converging at the axle. When you front steer a car, this triangle must be retained. This is in big part why many front steer rack conversion with stock lower ball joints fail...they actually create reverse ackerman. This is where a divorced steering arm could allow a configuration for rear or front steer. Zero ackerman is preferable to reverse and some competition cars actually eliminate ackerman. A divorced arm could also be built with a slotted tie rod mount to provide further adjustment. Many oval track arms utilize this feature to adjust the ackerman angle further.

The dwindling supply of OEM parts and limited reproduction s is why I would consider a fabricated arm in both upper and lower. As you point out, oval track hobby racers have created a horde of cheap parts that are easily replaced.

The upper control arm pivot point isn't impacted by caster, but it is impacted by anti-dive. Since the front pivot is higher that the rear, you have to calculate the dynamic pivot. T=Looking down on the control arm, this is done with a straight line between the front and rear pivot. Then create a 90* intersection on this line that extend to the center of the upper ball joint. This position is the dynamic pivot of the upper control arm.

Overall your layout appears to be on the right path. When I plotted my Challenger, my roll center ended up at 5.5" with 26" tires and the earlier disc standard height spindle. Since I can't access the program, I don't have data on my various pivot point positions. I did drop it down until the lower arm was at zero ride height, or the ball joint is perfectly level with the inner pivot.

I know Dr Reed always tried to target a 2" roll center height from his Mazda days. I think that will be really tough to get with stock pick up point Mopar. In my oval track days, we typically tried to get to 4" roll center for the front using stock stub cars. We also created offset centers and cantilevered pivots since we only turned left. In comparison, a street car is easier, everything simply needs to be a mirror image.