If it is a 64 small block it has the 5-bolt bellhousing pattern, same for a 65.

Two choices for bellhousing - manual or C4 automatic. Any C4 will bolt up to the automatic bellhousing. These bellhousings are advertised once in a while. There is one on Craigslist in Spokane for $200 that went up this morning.

Ford also had the Fordomatic 2-speed auto but it has an integral bellhousing that is 5-bolts.

The 260 is a good little engine but not much of a power producer. Depending on what you want, and want to pay for, starting with greater displacement is probably a good idea (it is a hot rod you're building..) as is a newer block with the 6-bolt bellhousing.

Hope that helps.

Andy