I want to buy an oil pump repair kit for a Ford N9 tractor (Serial #9N18515). I see that there are two versions of this kit (looking at https://www.just8ns.com/APN6600A-Years-1939-52-Oil-Pump-Repair-Kit and https://www.just8ns.com/APN6600B-Years-1939-52-Oil-Pump-Repair-Kit). One is with 9/16" Pumping Gears (Part #APN6600A) and the other set is with 3/4" Pumping Gears (Part #APN6600B). Both appears to be for 1939-1952 Ford N9 tractors. Is there any way to determine which one fits my tractor without pulling the oil pump and disassemble it?