Suspension too low

blueprint from the adjustable front spring hangers used on the australian Valiant charger RT suggest the holes should match the bolt you use for your 6 or v8 sized bushes.

3 parts need printing matching together and sticking..

might be a starting point

but keep in mind adjsuting the height of 1 end of the spring has an impact on under/over steer
which si why these had two holes one for twisty short track use and one for 24 hour race long road track use. the effectiveness potentially greater on the aussie car 8 inches shorter and 2-3 wider at the back

Dave
This is the quality of information I was hoping to see. Thank you sir. Those schematics are exactly what I saw making.

I've been thinking about it over the last 24 hours and there would have to be a difference in handling characteristics when changing the spring mounting point relative to the center of gravity. In this case, I would be raising the rear roll center by 1 inch while front mounting location of the unsprung weight of the axle remains unchanged, reletive to the ground. So a 1 inch increase in the measurement between front eye and it's connection to the subframe.... what change would that actually cause, can you even feel it in the seat? According to the file you posted, I think I might. I love science, time for an experiment.