pictured are the three 57 to 66 oil pumps. Before I start. Take note they all take a different length shaft, to compensate for housing height differences. The left is 59 to 61 (all rear sump engines. Center is 62 to 66 (only gs skylark had rear sump pickup.) To the far right is the 57/58. Those were the only oil pumps for the nailhead that I would consider to be crap. The vacuum pump was removed from the fuel pump from the previous years and now driven off the oil pump, and fed through a hole near the oil housing mounting boss. (Swipe right again.) Thats how you easily identify 57 and 58 blocks.. The vacuum pump can and will lock up and create obvious damage.. But even under normal use, it puts stress on the idler gear and forces it to orbit and wear, ruining the gear and housing. Swipe right for the video. Always inspect this when you buy one of these and you're cleaning the sludge out of the pan from lead contamination and deposits from crappy vintage oils. If the pump isnt damaged (its rare) then remove the key to disengage the vacuum pump from oil pump and live without it. Otherwise, the 59 to 61 pumps are a direct replacement on the 57/58 blocks. Those pumps are bulletproof. That being said, be aware of repro chinatown rebuild kits as the gears bind once the cover is mounted. 59 to 61 pumps bring a lot of money now, so another option is redrilling the block for the 62 and later and use a custom rear sump pickup we sell. Redrilling is also an option to turn all 57 to 59 engines into a center sump with 62 to 66 oil pumps, and visa versa. If your pan is ever off on an original late engine, I recommend changing the stock aluminum housing 62 to 66s with a cast iron new one, as the idler shafts on those typically slide upward and hit the crank.