the '65's vehicle identification says it came with a 3 speed manual. what kind of transmisison is this? and what are the benifits of a T5?

 

It's a 6 or 8 cylinder?

 

289 2V

 

You have a 3.03 HEF model 3 speed transmission (assuming it's original).

http://books.google.com/books?id=I8X...Ilu8rHHOsOeQaA

Regarding a 5 speed, the benefits are that it has an overdrive, allowing you to run a higher rear gear (more pep) and still keep the rpms down on the highway.