Tools, Sharpening and Power Machinery - replacing pump on old air compressor

I have an old Montgomery Ward 230V, 2hp air compressor. The pump has failed and I hope to replace it with a new universal replacement pump. Bought a $79 sale pump at Harbor Freight. However, the new pump is rated for a 3hp motor. I would imagine that the hp recommendation of a pump would largely be a function of compression ratio. So it seems that a too-small motor could overheat, but if the size of motor pulley was reduced, the motor would run fine but the pump would just not deliver air at the rated volume. Complicating my musings are two concerns:
air compressor FAQ's on this forum state that hp ratings on consumer-grade compressors are all but meaningless. Also, new pump recommends certain rpm for pump to be run. Should I calculate this from no-load speed printed on motor and ratio of pulleys, or do I have to measure it somehow under load? If I run the pump at 2/3 the recommended rpm, will it require 2 instead of 3 hp, as hp is a function of time?

You should be fine. Just a few questions, mostly out of curiosity. What size frame is the old 2hp motor, how many full load amps and what's the rpm? What is the recommended rpm on the HF pump?

Thanks for the reassurance. The new pump recommends 1050 rpm, with a maximum of 1200 rpm. As far as the other specs, I don't have them at hand. I'll have to get back to you Thursday after I have a chance to check it out. -Joe

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They seem overated. One electric horsepower should give at least 3 cfm at 90 psi. These fall slightly short in displacement and air delivery.

Knock the RPM down to 900 and run it up to 125 psi. It'll last longer.

Thanks to everyone who gave advice. Unfortunately, info. plate on motor is worn away, so I'm just going to try it and see what happens! Ordered a motor pulley slightly smaller than original, so that should give me enough speed reduction to run safely.
-Joe