Originally Posted by repechage

I have the same era Pinarello, a 57 center to top, I can measure it for you. rake and length.

There were no standard lengths. Builders did what they felt worked in their minds and this was before "forks-R-us" buyout carbon forks encouraged some uniformity.

In general bikes were designed with a level top tube in mind, but I have a few and seen many examples with factory components that did not have a level top tube.
A 3 to 4 mm difference will probably translate to .25° change in head angle as a rough guess.