Gauge cluster Question

[BoeJaker1976]

Hi there guys, This is my first post, anywho, Im here, stationed at Camp Humphreys Korea, And i'll be home on leave in a few weeks, and i have a 1976 silverado stepside waitin for me in my uncles garage. But, I always wanted to have a tach in the truck, but i dont want an aftermarket tach. The current cluster i have is the one with the big gas and big speedo, but ive been lookin at tachs clusters from 79, 81, etc. trucks, and i want to know if i were to get one that has an electric oil gauge, would it work if i bought a new circuit board in the back of the cluster and just changed the gauge to a mechanical one, would it work?, also, does anyone know how the wiring would change if i got a newer modle cluster? or do the wires need to be cut and rearranged in some way to make it work? Id appreciate the help, thanx