If you are like myself and trying to keep cost down but not performance while converting your Driveline from closed to open you might consider this method.
When converting my 51 pickup to open Driveline, I went to a Boneyard and found a GM rear differential from a 71 Olds. 272 gears for $100. Spent another $100 rebuilding and replacing bearings etc before install. I knew that if I wanted to change the ratio at a later date for other applications, I could easily buy a set of new gears to fit my new application.
My main goal was to keep the width as stock looking as possible.
So I cut a stick exactly the width of my stock rear end to use as an exact gauge before going to the Boneyard. Takes a lot of guesswork out of the equation. Hope this helps answer some of your questions.
