Ok I have had to d a lot of research on the subject at hand not to replace a 216 with a 250 but a 261 with a V8.
The bell housing that is most common and will be easiest to find would be any truck from 55 second to 67 with a V8 or any truck from 64 to 67 with an l6 in it. This will give you a bell housing with the side mounts for the cross member under it and the correct pilot hole for your transmission. The later 68 to 72 will also work but you will need an adapter ring that fits around the transmission pilot bearing support to take up the space left by the bigger hole in the later bell housing. These adapters can be had from Novak for $30 some; it is a simple ring that fills the gap.
