Mechanical fuel pump

You can't always get the correct pump for older cars at the auto store.
More often than not they are incorrect. Although close enough to "work" and normally work well enough for most cars runnin around on the street, there were MANY different part number pumps for different pressure and flow ratings for different applications even in the same year model. The aftermarket in its infinite wisdom chose their one style fits all mindset and "what you get" is "what you get".