A friend of mine is rebuilding one of these at the moment. He's going the Mopar stroker crank route together with .090 over (!) to give 402 cu in.
There's been a couple of articles about this in Mopar Muscle magazine together with all the bits that interchange from the A engine. The heads look real trick and in the 402 size the engine is reputedly good for 500 hp.
I've attached a link that gives some of the basics...
http://www.1962to1965mopar.ornocar.com/poly318.html