rev counter position

[alan 122s]

I have a 123gt rev counter I'm thinking of fitting in my b21,can anyone tell me where exactly i should drill the hole in the dash to fix it to and what size hole neeeds to be drilled. Ive seen pictures of the general location but without sounding too picky can anyone measure where theres is located so i get it virtually right?/ thks

[222s]

If your dash pad is in good condition though, the tacho could always be mounted on a bracket off the A pillar (in the corner of the dash / screen) instead - I believe this is where they were mounted on the race & rally cars (maybe also the Ruddspeed tuned ones that didn't have the complete dash panel??) prior to the introduction of the 123GT. It would certainly be in period & also be easily removable.