Quite a few actually.... To be clear, do you need a clutch fan (fan blades), or a fan clutch (what the fan blades attach to)?
Assuming it's the clutch unit, your '71 is probably like my '72 K20. Factory 7-blade fan with a 2 1/2" pitch. If so, it should use a HD clutch like the factory one. HD ones have fins across the front, and standard-duty ones just have a ring of fins around the perimeter.
A few months ago I replaced my leaking OEM fan clutch with one from my local NAPA store. Made in Texas by Four Seasons, NAPA p/n 271303. It's a perfect fit.
Oddly, most aftermarket outlets don't list a HD unit for my truck. We had to look up a mid-to-late Seventies K30 to find the correct HD unit.
Good info here including differences between standard & HD,if you're interested:
http://www.haydenauto.com/featured%2...s/content.aspx