I googled <aquarium pond pump + "head height" + "flow rate" + name of pump> when I was shopping for my pump, that was how I found the Mag Drive table I posted.
But I agree, google also throwns in a lot of junk. And many of the flow charts are scanned as a picture, so that is not picked up by google as well.
As for Ebay pumps, if they don't specify a make, I would be suspicious of its origins ... likely some no-name knock off that is not worth your money!
80 gal FW with 30 gal DIY wet/dry/sump.
9 fancy golds, 1 hillstream loaches, 1 rubber-lip pleco (C. thomasi), 3 SAEs, small school of white cloud minnows, planted.