Cooling Fan speed?
Till the fan comes apart.
Not being a ****. I just have not seen any speed ratings on oem fans.
As is you are overdriving the fan by about 40%. So if engine is 5000 RPM fan is around 7000 RPM.
On my stock 273 the fan and crank are much closer to 1 to 1(IIRC)
Typically in a racing setup the fan and alt pullys are larger in diameter than the crank pulley to underdrive them