1948 59 A-B fuel pump pushrod-which one to buy?

[PGBuick]

I acquired a newly built 1948 59 A-B V8. I have the fuel pump stand with pump attached (came to me off the motor) but there does not appear to be a push rod for the pump. The intake is a stock cast iron single carb for now. How do I know which length pushrod to buy? They appear to be readily available from several sources, including Speedway. Brief research indicates the 8 7/8 would work. Is there any way to confirm this? Is there any adjustment needed on this pushrod when installed? Is it just the pushrod that goes into the hole, or are other parts needed such as a retainer, or other pieces? Thanks all. Pat