T-birds were thunderjets. They are still very impressive but not the same internals as a cobra jet. Cobras bring much more cash. Thunders were non emission engines and from what I have read, using the heads on the 460 is the way to go. I myself would just run it the way it is. I doubt you would be disappointed. Others could tell you where to find a standard bell housing. As far as I know, the majority were automatics.