More internet searching turned up a guy that made his own dual pulse capacitor discharge welder. We passed a few e-mails back and forth, and I was able to buy one of his unpopulated Mosfet power switching PC boards for a reasonable price.

I ordered some components and built up the board. I was not able to find the power Mosfets that he used, so I got some that had even lower RDS on and higher current rating.
Before trying the board, I decided that It was time to do the capacitor bank over again, with a more compact form factor, and aluminum buss bars instead of copper, as I was concerned about passing the high current across a dissimilar metal junction.
I used 3/16 X 2.5" wide aluminum plate to make the buss bars, and tied them together with more 3/16 aluminum. To make the lowest resistance joints, I welded the joining buss bar to the main buss bars, around the periphery, and through 5 through holes on each bar. Should be ready to try it out in the next couple of days, as I have three MIMA systems to build first.