VM is finally back up and was able to check some photos.
I don't think those spindles are swappable.
The splines on the spindle of a 64 are mostly above the top of the pulley because the mating spines are at the top of the pulley.
The splines on the spindle of a 1435 are mostly below the top of the pulley because the mating splines are at the bottom of the pulley shaft.
So, spindle lengths are likely different and spline lengths are also likely different.