You didn't say what transmission you have.
The original manual transmissions all used a bell housing with side motor mounts giving your engine four mounting points, two at the front and two at the bell housing. If you are using a newer automatic with just a tail shaft mount you will need to convert to side motor mounts with the universal crossmember sold by many of the truck vendors.
Side motor mounts were first used in 1958 on the passenger cars. Trucks and Corvete's continued to use the front motor mounts for many years beyond.
Mike B
