They say it used a TH400 tranny. I will bet a crisp $10 bill that it was in fact a ST400, the Buick version of the TH400. I say that because the ST400 was used by Rolls Royce at that time! The nailhead Buick ST400 has a very short bell housing as the torque converter sits inside the block on the Nailhead not hanging off the back like a Chevy. So the transmission is a perfect candidate for an adapter to other engines. It has been used in the Aston Martin as well and I believe even Ferrari used the Buick ST400.