Buy a used tach or new tach

Yes. It's just squeezed up in there. I suppose you could fabricate some kind of strap to go across the back to keep it from backing out but the foam I used was some kind of industrial stuff like insulation. It was in the trunk of a car I bought so I don't know the origin of it. I suppose you could wrap the the stuff all the way around and it would work just as well as long as you can stuff it in there. I just used the three pieces to keep it centered and as dense as it was, I was afraid I couldn't push it up in there if I used too much.