The 2947 is the smallest clutch unit you can get that will do the job. When I got my '70 Duster, it had a Champion radiator with a 5 blade fan and no clutch. I removed the fan and spacer and installed the Hayden 2947 with a 7 blade A/C fan from a 440 car and it works great. Moves a ton of air without a shroud. Not much clearance between the radiator and fan, but you don't need much either. Yes, the clutch bolts were a challenge to install, but got it done. Temp on stock gauge runs a bit less than 1/2 consistently at 90* ambient temp with high flow 180 thermostat.
