I think the T5 is a good choice. They evolved from the Borg Warner T89 that was used in the Ford police interceptor and GMC used it as a heavy duty option over the Muncie. They are not for a muscle car application, but will work well in your application. However, they come in different ratios. Overdrive can be anywhere from .72 to .86. I would look for the .72 or .73 ratio.
