The mid 80's S-10 is the most common. The 88 up S=10 is a good one but has electric speedo drive. You would have to use an inverter or custom gauges. There is a tag on the rear housing under one attach bolt. It has a bunch of numbers but find the one that starts with 1352-. The 3 didget number after that ID's the tran. Usually 145 on the mid 80's trans. If you log on
www.mongosgarage.com you can ID. it. Like Moneypit say's you want to pick a ratio to match your engine & rear end.
