Thanks for the suggestions. Unfortunately, no one had this particular tach. I had to order one from the UK. If anyone is doing a Mod on TIIIs, you may want to hold on to the tachs since they are hard to find.
I was very surprised myself, this tach is very special with an output of 20 volts per 1000 rpm at .2 amp and the TIII is very sensitive to receiving the correct voltage. I tried using another tach that was close and modifying the voltage though voltage dividers but I couldn't get it to work properly. There was a possibility to do a special build but the lead time was too long so I had to do the alternative. Now I know for the future. What's really bad is I've probably thrown away at least 6 TIII tachs from mods in the past 5 years.