Just purchased and swapped in a "racing build" SBC350 into my 78 LT. Little did I know what this meant. Supposedly compression is upwards of 10.5:1. I've been told to use racing gas only- 110 octane- by the builder. Is this necessary, or can I get away with 91? Or perhaps use additives (which I know is frowned upon?) I know that using the wrong octane can cause detonation problems so I'd rather avoid the death of my new engine before it makes it out of the driveway. If it makes any difference, the build is as follows: forged factory crank, forged piston heads and rods, mild cam, ported and polished 76cc heads, copper head gaskets, Gen2 intake manifold. Better yet, the old quadrajet that came with it was crap. I'm (temporarily) running a 500cfm Rochester dualjet. Do I risk running too lean on this carb? On a regular 350 street application 518 is decent, 650 for racing...again, I've been told this is a "racing build" and that it absolutely needs a bigger carb immediately.