<VV>Tachometers

[Padgett]

>It is difficult ($$) to modify a tach that was designed for a set numbers 
>of cylinders to match another,

Is one reason why I stay with GM factory tachometers for the most part. 
Except for the encapulated 90 degree sweep units GM used in the early 60s 
(and then it is a matter of knowing where to drill a hole) on the 
D'arsonval movement (270 degree sweep) tachs used until 1973 it is just a 
matter of swapping the capacitor: .33 uf for a V-8, .47 for a six, and .68 
for a 4 cyl.

Padgett