I wouldn't unless you run electric fans. You could see the same gains by using stock pulleys and running a properly designed performance crankshaft damper. Dyno proven power gains over OE rubber dampers, on multiple ranges of engines through work.
Plugged heater core?
When was the last time you flushed the coolant system?
I'm getting ready to do a 3 core radiator install in my 64 and I preemptively ordered the jag clutch.