[AngryPirate]

Basically, I chased down the distributor part number on rock auto and it pointed to a distributor for a 1964 GMC 1000, but none of the caps matched the distributor (distributor had holes for screw down style cap and the caps shown for the 1964 were the type that have the arm that slides under a lip on the distributor body (wrong) ).

I dug a little further and found a distributor contact (points) that matched mine on rock auto, so I search amazon for the points part number, and low and behold, the amazon 'commonly bought together' section showed a cap that 'looks' similar to mine. I'm still doing research on this, but it looks promising.

It is nice to see that petronix or at least in this post they identify a larger and smaller distributor cap and one with a window (larger) and one without (smaller). Mine certainly doesn't have a window and is the smaller of the 2; so at least that lines up.