retrofitting a tachometer?

[lunarhighway]

i'm looking at getting a kit for a digital tachometer.
it includes all components needed to build a basic two digit tachometer that counts the pulses behind the breaker....

this could be interesing to determine certain shift points more eccactly.
and the two red lcd digits will blend nicely in the 80's interior.

however i'm wondering what other options i have. i assume there's ready build tach's available analog or digital, as i see them om tuned cars but i assume they're pretty pricy, and i'm not sure where these hook up? i could also try to find a donor part maybe but ince they're ussually part of the complete dash that might not be easy.

does anyone have any experience with retrofitting tachometers? any advice is much appreciated.