[ChevyTech]

Badass66ss have you tested the compression on all cylinders of this engine?
If not it would be a good idea.

About the fuel you use:
The TBI 350s have a 9 to 1 compression ratio.
The TBI 305s have smaller combustion chamber heads with a slightly higher 9.3 to 1 compression ratio.

I have found the 305s will run best on the 89 octane rather then the 87 octane ethanol blend they sell here. I have tried 91 octane in my 305 and found it ran best on 89 octane.

The electronic spark system will retard the timing if it detects pinging. If you advance the timing from spec the spark control will remove the excessive timing when the system is warmed up and running in closed loop operation.

When I run 87 octane in my 305 during the summer I can hear an occasional ping and the system backs down the timing to the point I can notice a lack of performance. I is much more pleasurable to drive with 89 octane and I hear no pinging. The performance difference is noticeable.