which S&S oil pump for S&S cases?

Howdy all,
I recently purchased a set of S&S big bore cases, I am in the process of making a parts list. I found the code (SO) above where the oil pump locates and then cross referenced to the crankcase style designation code and found that the oil pump I need is listed as "spec".
can anyone please tell me what this means and what pump I will need? is there another pump that will fit?
thanks in advance.

[Pa]

Email this address sstech@sscycle.com for answers to your pump questions. Regards, Pa

I Got this sorted, the cases took a 65-69 pump.