What size compressor should I be looking at to run a wrench rated at 450? This old fart is tired of trying to break free lug nuts. Thanks.

 

I just looked at McMaster-Carr's website and they show some impact wrenches at about that torque using an average of 5 cfm.
McMaster-Carr

I was tearing apart the suspension of my '90 F150 last summer and I went to Sears and got the strongest impact wrench they had by Ingersoll Rand. My compressor is also overkill being the biggest Ingersoll rand the Sears store offered a couple years back. I think it's 10 cfm at 100 psi, but the pressure can go up to 150.

 

A lot of light duty compressors are set at 90, but you can run them up. 150-160 is good.
I run my compressor at about 150psi and my cheap impact does a good job. I also use a battery powered Craftsman 19.2? and it's good too for lug nuts.