The 470 was built from 1976 through 1984. The drive is an early design Alpha One. This drive was sold as a pakage from Mercruiser with a 260 HP 350 Chev. from 1978 through 1986. It will handle 300 HP IF it is in perfect condition. If it is a 1976 with original gears and shafts and 28 years of use You can expect a failure in the near future.
The Chev. bellhousing will bolt up to the transom plate with no adapters. You will need the correct flywheel, engine coupler, and front mounts.
Hope this helps.