4 speed swap from a 64 to a 70

the parts will fit. however, the 64 has a 12 " dia flywheel , and a 9 1/2 " clutch. the bellhousing is smaller versus a 340 bellhousing. the 340 used a 13" dia flywheel and a 10 1/2 " clutch. the 64 has a ball & trunion u-joint, the 340 had a slip joint style. the trans crossmember is different. to make it correct, have to change trans tail housing to later A body style for slip joint.
If you have a 727 trans, the drive shaft will be too short for the 4 speed trans. the bellhousings are made for specific flywheel diameters.