Sometimes I get stumped by the easy stuff! Do I measure pulley width at the bottom of the groove or at the top? On my '48 Chevy 1Ton with the screaming pump, the original 216 has been replaced with a 1953 216, serial number LBA216243. The belt is 5/8" wide at the top but sits a little proud of the pulley so I'm thinking I need a smaller belt. I see both 3/8" and 5/8" pulleys listed for the '53 model engines and I'd like to get the correct pump and belt. Can '48 pump be used on a '53?

Thanks in advance for the advice! Jim