1950 Oldsmobile 88 service manual (p. 16-25), it states -
45 AC spark plugs are used on 6-cylinder engines (does not apply)
46-5 AC spark plugs are used on Rocket Engines (8 cylinder)
Plugs are metric 14mm, 13/16 hex body
Proper gap setting 0.30" for eight cylinder model
Replaced at intervals of 10,000 miles