Re: What size fan?
ah! I apologize. I misread that. I now see it's just the shroud you didn't purchase.
Normally, the radiator will dictate the OEM shroud you can mount and that will dictate the biggest fan you can fit. The BB and SB radiators had different shrouds and they are not easily interchangeable. So you want to confirm what your radiator was built for. Then you should be all set to choose the biggest fan with the most blades. Either way, I'd go with the 6 blade AC fan or an aftermarket copy as mentioned in some of the above posts.
Fool around, Get hurt, Don't come cry'n to me.
Pypes Performance Exhaust
Cold Case Performance Radiators