Fireworks under dash

Got home from work today, and it was a cool 63 degrees, perfect for a drive. after a 5 mile warm up, I turned the corner and decided to give it the berries. Got an original AVS rebuilt by Fishy68 and it has no bog at all, so I'm like a kid with a new toy. Lo and behold as the revs climb in 1st I see sparks and what looked momentarily like flames shooting down on my foot like a roman candle. I assume my accelerator pedal frame made contact with a bare wire. Its almost dark and with a flashlight I couldnt really see any evidence of arcing, carbon, etc, when I got home. Waiting for tomorrows daylight, but in the mean time, I'm left wondering. Whatever it was, it wasnt a cigarette lighter wire shorting out, it was major current. Till then anyone ever experience this? Any educated guesses? Thanks.
360 dart, column shifted 904, manifolds, stock exhaust.