Although the forward housing on the '65 Gran Sport ST 300 is different than the BOP ST300 at the top. Is the housing to engine block bolt pattern the same?
The Nailhead bell housing bolt pattern is different, so the Buick/Olds/Pontiac bell housing bolt pattern is not the same. There are adapters.
The only adapter I know of is the one Jeep used from 65 to 72. Jeep actually used the Nailhead Buick ST400 transmission, which required the adapter. Jeep even used the Buick 350 engine. More info here, scroll down to see the post by Zman: https://www.jalopyjournal.com/forum...r-buick-trans-setups-nailhead-adapter.155680/
