[Brian]

The 59-64 generators will share parts with the 39 and later 6 volt, 2 brush generators, NOT your 3 brush. So...what you want is to find a 39 Standard generator to use in conjunction with the later 12 volt affair. A 39 standard has a generator mounted fan, therefore you use that pulley, the front bearing retainer/gene mount, and the armature, body [with fields] and rear brush holder out of the 12 volt generator.