Jack,
Lowering the front of your car will change the toe setting in an outward direction. You will have less toe in, and will probably have toe out. You need to have the toe reset.
The stock '71 front upper a-arms do not have shims for adjusting caster. They also do not have the larger "s" bend in the rear channel like the later cars have. This does not allow for the typical modification to be done to increase caster. Offset bushing are available.
Front wheels wider than the stock 7" will also cause the car to pull under heavy braking.
Get the toe set and then road test again. Have the caster checked and let us know what it is. Since the caster is non adjustable on the '71 cars (with stock a-arms), most likely the caster will be 3* at best, and will probably be less. You will probably find that the right side has less caster than the left side.
John
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