The problem with the original wide range humbuckers is that the magnets are the pole pieces. The magnet material is CuNiFe. (Copper, nickel, iron)
This material though still manufactured, is rare enough that it is quite expensive, also it is not being used currently for magnets. So you would have to buy a sizable quantity of this material, made into rods, and then have it polarized and magnetized in a separate process.
Also, this material is not very good at holding a magnetic charge for a long period of time. It is estimated that in the original wide range humbuckers from the era you describe, the CuNiFe pole pieces have lost 60%-70% of their magnetic power from new.
Rewinding isn't going to help you there.
I too would like to know what to do to replace a wide range humbucker.