You have an absolutely beautiful car. Very clean and well done.
You can reach your 400/400 goal with any of the ways you mentioned. If your going to run it hard, you'l need to upgrade the bottom end. It will last a while at those levels, but it's days will be numbered.
For a NA 383, you're going to need 10:5 comp, pump 93 gas, heads that flow 260/200 or better, 240-245 duration cam, 1 3/4 headers with a good exhaust, air gap intake and a 750-830 carb. It may be a little less streetable than your current setup, but not much.
It really comes down to which route you like the most, and want to pursue.
John