Jack, thanks!
Okay....I'm pulling a little over 2 volts at the tach output, which is good news (should be between 1 and 5 volts). At least that tells me that the MSD box tach function is working. I'm now 99% confident that the tach board is fried and needs rebuilding. I'm sending the unit out tomorrow to "MO-MA Instruments" in Albuquerque, NM for some higher quality "German" circuitry work. It was either that or send it to some outfit in New York (in which 3 people I spoke to there gave me 3 different answers and 3 opinions).
-Deano