I started having exactly the same trouble on my 235. I tried changing carburetors and bought one of Tom Langdon's Holley/Webber 2 bbl carbs and converted it. It's never run so well.

My thought is that the Rochester 1 bbl carbs don't have an adequate accelerator pump, causing a lean condition when the engine demands more fuel. The fact that it runs better with the choke pulled out a little seems to support the assumption that maybe you're running lean all the time.
I guess you could rejet your Rochester, and have it rebuilt. I didn't try that with mine. I just replaced it because I never liked it anyway.

You think you might be running a bit lean?

52 GMC 3/4 ton pickup
68 Big Block Vette
68 455 Firebird