There is a plug behind the instrument cluster for a tach but that usually has other wires that attaches to other things in the cluster. If you buy a used toyota cluster for that year you can simply transfer it over. After market will have good instructions. you will need a wiring diaghram for your truck. This link will help
www.customtacos.com/tech click on interior/audio tech and then mini tach install. You don't have to install at the ecu harness, instead tap into the wiring harness at the cluster. It's usually the black wire coming from the igniter. have fun.