Mechanical Rev Counter Drive

[SanRemo78]

A bit off the wall this one.... I'm attempting to connect a mechanical rev counter to an Alfa 164 3.0 V6. I've seen plenty of old Alfa mechanical rev counters on Ebay and wondered if anyone here had any clues as to how they are driven and what components are needed? If there is something that will bolt straight on somewhere then that's the route otherwise I think I'll be looking for a scrap dizzy from a 3.0V6 75? Anyone got anything that might do the job?
Cheers
Guy