I think Big Jim is correct, I didn't really notice a big difference from the properly working stock distributor when I installed the HEI.
However, when I started having trouble with the distributor advance not working properly and ignition module failing intermittantly, I wanted to simplify things so I switched to an HEI (all ignition components in distributor, and 1 wire hookup)and removed the computer.
That was before the MC2100 swap (still had the BBD), and the two worked together with no problems.
Right or wrong, my distributor advance is connected to manifold vacuum, and runs great. <img src="/forums/images/graemlins/patriot.gif" alt="" />