Rick - the MSD part number is MSD-8431. Here's a link to the Summit Racing page with a picture of the cap:
http://store.summitracing.com/defaul...&part=msd-8431
Notice the red piece of plastic on top of the cap (that says "MSD"). You do not have to use this piece.
As for the original black cap, I couldn't ever find a replacement part number so I ended up with the red.
Scott, SPF#1230