Electronic Ign/Hei/Ballast Delete Wiring?

Are you just using the Megasquirt for the timing capability or is your engine fuel injected?

I got the impression he is going to use it for timing first and probably EFI later on.
FYI, in case you didn't realize it your HEI kits is also capable of the same thing.
The Megasquirt instructions lay out the diagrams and programming procedures for it on their website.