Stock 340 flywheel limits

I have had my stock 340 flywheel to 6800 rpm's sustained for a good long bit. The idea of that exercise was to find a top end of my car at the time. Just how fast could I go. So I floored it and I left it in fourth. The engine was running at 6800 RPMs. And that was it.
my question ,usually is, what's your legs worth?