Fortynine5 -
I agree with the comments Fla54Chevy3100 has made. I also agree that a 1/4" to 3/16" spacer would solve any problems and could be used without any consequences if you interested in being sure that a one time installation of the T-5 and other components was what you were looking for. I think I would be willing to test it without the spacer before I decided I needed it. If I did, I agree 100% that the spacer would be my choice before I tried to do any "machine work" on the input shaft with a grinder or Dremel style tool. On an older truck, such as my 37, I had to use an adapter plate in order to have the correct bolt pattern. That adapter plate, 1/2" thick, took care of any triming of the front of the input shaft and lengthing of the splines. It slipped right in and everything worked as it was supposed to. All I had to trim was the throw out bearing retain, which is the easiest of all alterations.
Joe
