Do they look like the one Mike's has to sell or the other parts from of the parts fischeShouldn't be the same. From the factory 75 are off on reserve with the closer bolt spacing 80 are vacuum with wider bolt spacing. Parts don't interchange.
Many have converted the late vacuum to aftermarket off on reserve from MikesXS and other vendors with similar.
I buy my petcock rubber "valves" from yamaha always found the aftermarket were too thin.