I did some shopping around and went with an off-the-shelf Techtonics unit. (Mine first one is an OBDII car.)
After some telephone conversation, they raised the rev limit (not because I'm making power above 6K with an old engine and the exhaust we have, but to get it out of the way), advanced the timing more and earlier, and pretty much left the mixture alone. They don't lean them out for road racing, because we spend so much time at WOT.
They indicated that, once we get the spec settled and can dyno the thing, they can burn custom-tweaked chips to tailor the mixture more closely.
Things might be different with the earlier car, of course.
K