He advertises in Lawn and Garden Tractor magazine, thats all I know about him. His prices may be to good to be true, or like was said, he buys in BULK and has minimal overhead. To be honest it will probably be a couple years before enough of his stuff gets in circulation to know if it is any good.
I used Jmech's supplier for piston and rings for my Magnum. Parts look good, no name on anything though. I did find a machining chip in a piston ring groove, no big deal as long as you look at your parts.
Here is my take on what "grade" of parts to buy. If you are going to run the crap out of a machine actually using it and using it a LOT, then use OEM and leave no stone un-turned. If you won't be running it a whole lot, go with mid grade. If you won't run it 1 hr a year and that will be only to load an unload off a trailer at an antique show, use the cheapest parts you can find and pour your money into paint.
Back to your question, I too wonder about the quality of his parts because those prices are mighty tempting.
I'll be glad to hear reviews on his items, good or bad.