According to Tom Langdon, Holley Webers out of the box are good for about 200 cfm. My experience so far with two of them on a 320 cid GMC appears to confirm that. At 4,000 rpm your 292 will need 338 cfm. Two of them should work well for you; one is not enough, unless you are proceeding slowly by design.
God's Peace to you.
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