To Stroke, or not to Stroke

I'd run a different camshaft. Unless you already have teh 509 cam, I'd look elsewhere for a camshaft. There are much better cams available than the .509. Plus that 509 will act like a much smaller camshaft in a 500" engine. You can put a bigger cam in the engine because the cubes will suck up lift and duration.

You don't mention convertor/stick?

Anything from a 470-512 using the B block is a good deal.

There is at least one 71-72 Dart running 11.50's with a 400 engine around. Not sure if 383man from the moparts board is over here. His son has a 400 in a Dart that runs that number.