15" fan seems a little dinky sized IMHO. The performance small blocks of late 60s used an 18" fan, typically with a clutch. I used an 18" fan setup with a 1990 shaguar XJ6 clutch Hayden 2675. Since the diameter is bigger than sections of the radiator I had to make my own shroud. I used a homemade wooden buck, and an old cotton T shirt as a basis for it, then fiberglassed it, bracketed it.