Fan VS Fan

Actually it's the same fan (Flex-a-Lite 400 series) that Summit sells for $16.88 and it's rated up to 8,000 RPM and comes in sizes up to 18' diameter.
I'm not sure why that link I posted above to Flex-a-lite said it's for a stationary engine, because here is the same fan on there site again saying it's ideal for a race and performance engine http://www.flex-a-lite.com/auto/html/400-series-economy.html
I guess they're just saying they recommend it for either setup.
I understand about the fan bite effecting HP, and these don't look like they have too much of a bite.
Maybe I'll try to pick one up at the next swap meet, there's usually someone selling them.