The clutch in the pic is the thermal type which is considered most preferred. Depending on the rest of the cooling system, the 5 blade fan may do just fine in your app. Bouchillon sells a 6 blade that they swear by... may be the same as the one in Amazon.

Personally, I'd go ahead and use the clutch and fan pictured. There is a good chance it will work great. If you do need more fan, look for a 7 blade in the JY. I have a big 7 blade from my '78 Cordoba core BB engine. I don't use it because the 5 blade "low drag" that comes with the MP kit works great in my setup.