You've got an 8 cylinder engine, and you want the Volvo tach in the dash (the 30mm tach in the center under the speedo) to work with it?

Am I missing something here? The connection is straightforward -- a wire from the ignition coil through the bulkhead (one of the rubber plugged holes will do) to the tach's input -- later cars had such a wire built-in, but I can't say about the '80 model year.

But in any case, the Volvo tach is a 4-cyl. tach....
[I don't think any wagons got Volvo's PRV V6 engine, so it's not likely to be a 6-cyl. tach.]
.... so it will run 100% too high. For every two revolutions of the V8's crankshaft, it will generate 8 pulses from the coil, while the 4-cyl. tach in the car is designed to interpret every 4 pulses as 2 revolutions, so the tach will indicate twice the actual rpm of the engine.

I would think this is obvious ... so what's the point of the question??? Instead, I would expect to see a 8-cylinder tach installed. Right?

Regards,