I highly recommend Mr. Langdon's mini HEI dizzy. I just bought one a couple of weeks ago and WOW. What a difference. The 235 idles smoother and seems to have a little more mid-range ummph. I wish I had done it years ago. It is an easy swap, and looks original (to the untrained eye).

-Tim
'51 Chevy 3104 w/'56 235, 848 Head, HEI Dizzy, Corvette Cam, Split Manifold and Dual Carter YF's