What you didn't say is header or free-flowing exhaust.
Until you open up the exhaust, I highly recommend to not waste your time fudging with the Distributor. You will just get a lot of detonation and lousy fuel-economy.
The reason I'm fudging with the distributor is I already have "a lot of detonation and lousy fuel economy" (15 mpg in town). My goal with the distributor is to reduce the mechanical advance to eliminate the ping.
I have stock 2" exhaust all the way back. I think the Super Six cars came with a 2.25" pipe. I asked the muffler shop to give me a 2.25" pipe with a 2" muffler, but the guy convinced me it wouldn't make a difference. I think he was wrong and I am considering telling him to do it anyway. This is what I am looking at:
