I'm looking to purchase an a.i.r. pump for my 69 Z28. From the research I've done I looked for a 7801149 pump. I located a pump, it,s a June of 1969 date has the white fan, but isn't stamped with the 7801149 on the back, it does have the number 780650 behind the white fan and isn't a restamp pump. The pump comes from a reputable seller and he says that not all pumps had that 1149 number stamped on the back. The reason he's thinks that is because he has other pumps without that number that are original and unrestored. Whats do you guys think?