Here is adapter I believe you would need.
http://www.hotrodworks.com/catalog/...48-1983-chevy-pu-and-1955-1983-cars.html
Very good product. Mine fit perfect. By using this, you don't have to cut the tip of the input shaft. Keep in mind you will still have to unbolt the sleeve over the shaft and remove some material. I can't remember amount, but the measurments are in my garage. I cut it off by putting a stainless band clamp around it, using a sawzall, then filing it smooth.

Phil