parts-repairs
I'll add this to the MSD v. HEI discussion.
I have BOTH. The MSD is well made, works great for racing and also looks cool. The HEI clones with a tach drive use the same TYPE ignition parts as an OE HEI. The MSD tach drive distributors' ignition parts are unique to MSD.
If you're on the road with an OE HEI or HEI clone, and a pickup, coil or module fails, you can get replacement parts nearly anywhere parts are sold. That probably won't be the case with MSD tach drive distributor.
Doesn't matter if HEI has tach drive or not ... as there's a disparity in ignition parts availability between ANY HEI and an MSD tach drive distributor. Also, MSD's tach drive distributor requires an MSD or similar spark box ... and if the box fails, nobody but a coupla shops in USA can fix it and boxes are not readily available at just any old parts store. Bottom line ... if tach drive MSD fails on road ... you're probably stuck ... but if any HEI fails you can find "bolt-in, get it home" parts/service just about anywhere.
Recent rules in Nascar (cup, busch & truck) require all ignitions be located on top of dash. So now you can see the setup from the incar cameras' viewpoint. Look closely and you'll see TWO MSD boxes and TWO coils ... unseen is their race-only MSD distributor that has TWO pickups. This way, the driver can switch to another "backup" ignition system when the primary system fails ... happens routinely. MSD tachdrive dist P/N 8572 has only one pickup and a second "backup" pickup cannot be "bolted in." Of course, HEI cannot be readily setup with backup capability either ... but you don't see them in upper classes of Nascar ... nor do you see tach drive MSD in same classes. You can be sure those teams travel with many spare distributors, coils, pickups and boxes ... and there are plenty of trackside vendors with same. Let's not leave Crane out ... it makes & supports a redundant race-only setup too.
Both MSD and HEI are good systems. Either has advantages, limitations & risks. What's risky in one application simply ain't a problem in another.
JACK:gap