Can anyone recommend a good replacement pump for a 4840?  Are there any places online to stay away from?  What is the difference between the  pumps with serial plate and without?  The more I look at all the options listed for a 4840 the more confused I get.  My pump has 1 1/16 in inlet and outlet ports and a serial plate.   Will any aftermarket pump that has the same ports work?  Thanks!