You're making this harder than it needs to be. The upper A arms changed
early during TR4 production and remained the same through TR6
production. Changing the A arms gives you 3 degrees of caster rather
than 0 degrees. To make the conversion you change the A arms, the upper
ball joint, and the trunion, that's it. This will not change the
camber. If you want to change from the stock +2 degrees of camber
you'll have to do other modifications. If you lower the car 1 1/2
inches the camber will change to about +1.6 degrees, which is not
enough. If you want to get -1.5 degrees you need to move the upper ball
joint inward about 1/2 inch. The neatest way to do this is to redrill
the holes in the ends of the A arm. However, since the inner hole will
now be off the flat portion, you can add a small piece of pipe to fill
the space between the A arm and the ball joint surface. These
modification do not give you adjustable camber. If you want adjustable
camber like in the TR6, I believe you would have to do some major
modifications to frame members. This has been done, but most TR3/4
racers don't do this.
You do not need to change the caliper mounting plate to change the
suspension geometry. The caliper plate changed when the calipers were
changed from the early clam shell type calipers to the later TR4-6 calipers.
Larry Young
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