I have a '55 1st series with a '62 261 engine and a T5 from a '85 S10. We removed about 3/8 from the forward shaft of the transmission. It slide right in. Looks like it was made for my truck. You need to check that the clutch release bearing works properly. If you decide to go with a spacer plate, no machining would be required. The spacer plate requires special machining. There is a guy in Washington state. He makes the machined spacer plate. I have dealt with him in the past. He is a good guy with lots of knowledge on the modifications. Do not do anything until you talk with him. The web site is listed below.
Larry

http://www.inliners.org/buffalo/index.htm