Your definition of serious race effort is probably a lot different then most people not in the business. The most serious use of an MS3 I have found is Lee Sicilio's twin turbo hemi daytona that did 283mph on the salt flats a few years ago.

The support system is the biggest killer of the MS3, you can't phone up a hotline and get the help you need when you need it. That alone is worth the extra money for the Holley