100 Octane with 12:5:1 340??

E85 is like a program for a macintosh computer. It works AWESOME... for a hand full of people.

I'm still a fan, but I want a car set up for flex, which is out of the question with a carb. You'd have to run an O2 controlled electronic fuel injection and timing, with injectors that didn't hit static on the high end, but ran good on the low end for low octane.

Flex is the way to get some great drivability + high octane, but almost not worth it.

100 should be fine in a 12.5:1 if you have a good quench and blueprint your dist.