____________________________

Thanks KULKULZ!   Problem solved.  I switched the belt with one from another one of my cars and no screeching.  The defective belt looked brand new but there was obviously something wrong with it.  

____________________________

No noise with the PS belt removed so I know that the problem is either the belt or the pump.

Yes, I did want to make the 292 look like the original 256 including a minor modification to the 256 air cleaner so I could use it on a "modern" Holley 4 bbl carb. on top of an ECZ-9425-B intake.

Now you know I need to see a photo of that ...

Now listen, did you run the engine with the PS belt completely off and also the GEN belt separately (to isolate the PS pump and then GEN)?

____________________________

The pump is a 1954 and so is the crank pulley so the sizes of the pullies and the alignment match.  This engine did not always make that horrible noise.  Yes, I did want to make the 292 look like the original 256 including a minor modification to the 256 air cleaner so I could use it on a "modern" Holley 4 bbl carb. on top of an ECZ-9425-B intake.  Today I will first switch power steering belts with another '54 car I have and if that doesn't solve the noise I will switch pumps with my other car to confirm that the pump is the source of the noise.

Now did you run the engine with the PS drive belt completely off? That will differentiate belt noise or other.

What did the 292 come out of, PASS CAR or TRUCK?

If the noise is still there after belt re-install, all I can think of is that the 1954 256CI drive pulley is not the same size (width) as the PS pump pulley inducing slippage.

I am curious, when you did the 292 upgrade, did you want the engine install to maintain the original appearance of the 256?

____________________________

Yes, I used the 256 crank pulley and the bolt-on cast iron power steering pulley.  When I turn the pump pulley by hand there is some resistance but I don't feel any roughness.  

I sprayed the belt with water while the engine was running which did not effect the noise.  I tried loosening and tightening the belt. The noise is almost like a grinding sound. 

The spritzing determined if it was the belt and/or pulley. You need to remove the belt entirely and run. If the noise is gone, it is the pump.

Turn the pump pulley by hand (w/o belt) and see if you feel any roughness/resistance.

When you went with the 292, did you keep the 256 damper/pulley?

____________________________

On my power steering setup, an Eaton pump, I'm using an AX profile belt. A = 0.5 inch (13mm) depth is 8mm. As Kultulz points out if the belt is too narrow it may be too deep into the pulley. 
On the other accessories I'm using 2 of ZX profile. Z = 3/8 inch ( 10mm ) depth 6mm. X being cogged/toothed.
Don't know if the ZX  AX notation is a UK thing or you use the same.    
Good  luck.
stuey