I am coming late to this thread.
No advice on the Rochester B (other than replace it), but a few comments on the fuel.
As Jerry said in the post above, high octane fuel burns much slower than regular, thus advanced timing is mandatory, or a bunch of the fuel is going out the tailpipe unburned.
Don't take my word for it, but use Google or whatever search engine you prefer, and investigate octane ratings.
There used to be two systems of measuring octane; the (R)esearch method and the (M)otor method.
Of course, the supporters of each system stated that the system they supported was the superior system.
Finally, the government had enough, and did something intelligent for a change. The didn't support either group, they just averaged the two ratings. The new rating scale was called AKI for (A)nti (K)nock (I)ndex. Used to see at the pump the rating was listed as (R + M / 2).
93 octane on the AKI scale is about equivilent to 100 octane in 1954. Your Chevy will run MUCH better on 87 (or less, if you can find it) octane from a name brand station.
Alternately, you could disassemble the engine, install 14:1 compression pistons, a full race camshaft, etc., etc., etc. and just maybe the engine could use the 93 octane.
Put the savings in a piggy bank, and apply toward a Carter carb.
Good luck.
Jon
