http://cgi.ebay.com/STAINLESS-STEEL-REPLACEMENT-HEAD-MARCH-809-PL-/320559541364?cmd=ViewItem&pt=LH_DefaultDomain_0&hash=item4aa2d66c74#ht_500wt_891
Drop in stainless replacement heads for the March 809 pump. Commercially, the stainless March pumps sell for $250 more than the standard pumps. A replacement Polysulphone head assembly sells for $70. These heads come in at roughly $50.
These appear to come from a company called Chugger Pumps. Their website claims "chuggerpumps.com is a subsidiary of an industrial pump company that has been in business for over 40 years." Vague for some unknown reason. However a quick internet search shows that chugger pump is a registered trademark of Tri-State Pump from Farmingdale, NJ (www.pumps-parts.com), who also claim to have been in business for 40 years. So, they seem to have a decent pedigree, and are definitely not some fly-by-night company.
First off, here is the standard wet end head on the left, and the stainless one on the right. Look pretty standard on the outside, but notice that the stainless head has phillips screws. I like them better than the slotted on the standard.

Opening them up shows pretty much everything the same. The reason the stock head is brown is because of beer stone, its time for another caustic cleaning. Note however, the standard head has brass thread adapters, whereas the stainless head is threaded directly.

Closer looks of both impellers. The impeller in the stainless head is exactly 1 gram heavier.


Inside the head not much is different.


From the side however, it appears as though the stainless head has a better fit on the spindle. When you shake the two heads closed up, you can hear the stock head impeller knocking back and forth, the stainless one sounds nice and solid.

Installed, it definitely looks real nice.

The verdict. Appears to be a high quality replacement head for the March 809 pump. These heads should live up to years of service, and should be much less susceptible to breaking, and impervious to all brewing chemicals.