The way that the 6 sits in there puts the fan closer to the rad. So I am guessing that is why the 6 cly did not have them... Or at least I have never seen one. Oh, and the little 4 blade fan does pull good air.
On my little 64 with the 327, I have a 2 1/2 spacer and a flex fan. That is all I had at the time I put it in. Well.. It sits right even with the fan shroud. I have not driven it but it will idle up to temp and not run hot so I think I got it setup right now.
In the past we had a 283 and then a 350 in the truck and it always ran hot when sitting at a red light. I always figured it was because daddy had an old rotten Impala rad in the thing and no fan shroud.
