New guy to big block world, need a 400HP 383 Recipe
Welcome to FABO! Given your previous experience, 400FWHP out of a 383 won't be difficult, just read a few threads-you'll find plenty of builds that will exceed what you're asking.
I'm a fan of lightweight forged pistons- budget-minded Keith Black's are good;
FWIW, KB doesn't make forged 383 pistons, but their hypers are lighter than some of the other choices and they have HUGE valve reliefs...if you want GOOD forgings, shell out the ching for Diamond or go custom.
Stealth heads are a good upgrade from stock, but based on some other folks assessments on here, if you buy them assembled, take them to your machinist, have them checked for consistent installed heights, and good valve job and bowl blend. If you don't want to shell out the money, stock heads will just need some care...pretty much any route you go, you'll spend some money unless you know someone with a prepped set for sale.
Cams...man, there are so many from which to choose--the array is dizzying. I personally would roll with something a little more modern than the .509, but that's only my opinion. If you're not opposed to a solid, one of the other members here cranked over 500 out of a 383/432 stroker with a fairly mild build...good slugs, OOTB Edelbrock heads, dual plane intake, 750 carb...272/280 solid cam...
Carb, I'm inclined to go with the AED or QF recommendation. Edelbrock/Carter carbs are usually more docile for driving and tunable and I have no problem with them (I have a 1405 Edelbrock on my 5.2 Scamp), but Holley derivatives typically do better on the power...just depends on what you want.
What's you budget?
What's your intended use?