Does any ford overdrive automatic trannies have the same transfercase bolt pattern as the C6? I have a Gen2 doubler but want an overdrive to help battle high rpm.So will it bolt together? Also does anyone know of a shop that builds them to stand up to big tires and a healthy motor?

This has been gone over so many times, all ford T-cases from the vintage of the NP205 all the way through the new NVG271's have the same bolt pattern and input spline. They will all interchange.