Chris,
You needn't justify your choice to replace your factory tach ... but trying to pass off use of Autometer by current race teams as a preference [while getting sponsorship money] won't fly too well here, either!
Get REAL ... VDO tachs were good enough for the 917s, 936s, and 935s that won Le Mans multiple times!
There is only one Autometer user here that I am aware of in a vintage 911 racecar, and a few others that have used them in the past on other brands of cars. So, really, you aren't asking a question that many here have any experience with ...
The following thread has reverse-engineered documentathion for the 6-pin Bosch 0.227.300.004 CDI unit ... if you need information on the TD drive circuit in addition to the Autometer response to your question:
6-pin SC/Turbo CDI unit repair documentation
Consider yourself lucky that Loren didn't answer this thread!!!