[78-5.3]

ok i started my Cluster conversion i have the tachometer sitting in but none of the tabs line up ???? im gonna get some stong expoy ! any ideas??? im gonna use the factory tacho cluster fuel gauge in place of the oil gauge in the under right hand side of the smaller gauges !! my question is do i use any off the circiut board i will of replaced the oil , fuel , and add a tacho how much of the factory ciruit would i use??? oh my cluster is a 91 its going into my 78