Nothing has to be changed. Like fullthrottle said, the change from 27 to 30 spline is where the shaft goes to the bell on the birfield. It is a bit stronger but the real strength increase is the different metal that is used and the heat treat process that Bobby uses. I believe that he uses 4340 and 300m for the Longfields. Along with the strength upgrade you have the peace of mind that you are backed up 100% by Bobby Long. So far I know of only two failures on the 30 Spline Longfields and both have been replaced!
