So I ran some bench racing numbers, I wouldn't put too much stock in the actual numbers, but it can give you some relative idea of cost over change
Let's say your 401 inch 390 combo made 370 hp at 5200 and somewhere around 420 ft lbs of torque at 4100 for a starting point, that's assuming a 240 cfm head or so
As a WAG, the high compression version of the 422 inch 410, would probably gain around 15 hp and 25 ft lbs while shifting the peaks about 200 rpm lower.
If you adjusted compression as you talked about, which I think is probably wise, I'd say those gains drop 10 hp and 15-20 ft lbs with the peaks being the same as the high compression version
If you had the heads done with the 401 inch motor, with a realistic 260 cfm port. Your peaks would go up in RPM, but you potentially could make slightly more peak power than any of the other combos. Whether that meets the use of the car is up to you, but likely raises the peak power a few hundred RPM and really depends on how the heads were done and the rest of the build
So, it sounds like cost is afactor, porting a set of heads isn't cheap, nor is new pistons, balancing and crank work, so honestly I'd just go with what you have, it's a nicely matched combo that will run strong. As I said earlier, I think the 428 arm would be nice, and I think you'd feel it, but there is a reason people aren't doing it as much as they used to. The gains are just small for the cost compared to going with a 445.
For giggles a 445 combo with the same 240 cfm heads would likely only gain 15-20 hp, but would see probably a 50 ft lb increase. That's a difference you can really notice
I say run what you have, it'll be fun. Bank the money for the next round when you get used to it. In the end, if you are going to get used to a 401 and want more, the 422 wouldn't be much different IMHO
