I bought a monster tach and i need to know the easiest way to install it. Also where does the green wire go?
The green wire goes to the solid blue wire coming from your distributor. Here’s where I mounted mine, but check out the pictures in Dan’s profile, his shows it a little better.

What is a good power source to tap into?
-Steve
Jason, does that go for 90-91’s too. The blue wire on the distributor?
-Steve
For the 12v source I tapped into the power for my foglights. Yeah, I’m almost positive that the solid blue wire is the same for the 90-91’s.