[Lew Silverman]

I may have missed something here, but aren't you using the line-lock/low-side limiter for your burn-out's?

If you need a burn-out, launch AND over-rev protection, you'll need to follow Bob's advice and get a 3-step switch to work with your MSD and relay (although unless you'll be controlling a high-amperage circuit, you may not need one).

MSD has all of their wiring schematics, cross referenced by unit number, on their website, as well as a very handy smartphone app, to help if you need it.