Tried searched, but couldn't find this exact subject. Does anyone know the difference between an early '84-'91 and late '92-'99 Evo oil pump. Reason I ask is I have an early pump and a late engine (S&S 111, That I'm assembling. I'm assuming this would be a "later" style). Is it just a difference in the cover plate or oil passages in the pump itself.......or? Rather not buy another pump, if i can swap cover plates. The pump I have is a high volume TP unit. An S&S is some serious $$$. Good stuff, but rather put the money into the rest of the build.