[olddog]

I believe the 4.25 stroke crank is used with a 0.020" over bore to get a 482. That same stroke would take a 390 to ~440ish depending on the over bore. You could use the same crank in either engine but you would have to re-balance it (as in pay to balance it two times). One for each engine build.

Pay close attention to what they are saying on the heads. Yes you can bolt heads with smaller valves onto the 427 bore, but why do that to the 427 bore? The entire reason that engines were built with large bores and short strokes was to fit bigger valves. As time went on, the canted valves and hemi heads were also to fit bigger valves. Bigger valves allow more air flow, which allows more rpm, thus more power. Yes you can make up for the smaller valves with more cam, but the torque curve suffers, and manors, too. All this is in theory. You would have to dyno some otherwise identical engines with both valves sizes to know for sure what you are giving up. Blykins may have already done this and may share these numbers.

That said a stroked out 390 can be made to run fairly strong. You might find you don't need the 482. I would expect that a stroked out 390 would make almost the same Hp as a 482 with the same heads and cam. The 482 would make more low end torque and the HP would peak at a lower rpm. There would be some improvement because the bigger bore would un-shroud the valves and get a bit better air flow. At least this is all correct in theory.