As far as spring eye measurements go, with the weight of your car, they will differ. The flatter the arche under weight the longer the spring eye measurements.

If measured in a Flat plane the A body spring vs the 64-65 B body spring, the latter should be 1" longer.

But if its stiffer and it is, it can measure shorter in its arched position under a A body because of the A bodys less weight. mike