I'd suggest a 406 instead. Because there is nothing better than cubic inches, and the 400 will fit where the 383 will.
A good stock Chevy 400 block will be fine, two or four bolt main. use studs to retain the heads and mains. Align hone it and and deck it for square, then bore and hone with deck plates.
I'd suggest an Eagle forged rotating assembly with SRP pistons. Alternatively, I'd suggest an Eagle 4340 crank, with their 6" I beam rod, and SRP pistons. The I beam rod is plenty good enough and will save money. If you just buy the rotating assembly (more expensive, comes with 4340 H beam rods) you can get it balanced by Eagle and save hassle and time. You can even get it internally balanced for an affordable price.
I've not been happy at all with AFR lately, although I used to use their stuff a lot. I'd suggest a Dart or Edelbrock head with a 200cc intake port. I'd suggest 2.05 intake valves and 1.625 exhausts. The better the head flows without being too big, the less cam you need to make power, so you get more torque and driveability.
You'll need to make sure the head and piston you get yield about 9.5:1 or 10:1 compression, you can run that on 93 octane with an aluminum head. You want to get there with a total deck clearance of about 0.040", for good efficiency and resistance to detonation.
I'd suggest a cam in the 218 to 244 @ 0.050 duration area, with around 110 lobe seperation angle. It will work with the computer and have acceptable idle characteristics. If you can afford it, go retrofit roller, they are the ticket. I'd like to see around .480' to .500' lift with a 1.5 rocker, and I'd use a 1.6.
I prefer true roller timing sets, not the cheap ones. And I've come to like high volume oil pumps properly blueprinted, with the bypass dumping to the pan. With an 86 car, you'll need a different oil pan to use an early block, make sure you get a Corvette pan.
Edelbrock has some nice pieces for your intake besides the runners, if you don't already have them.
I'd suggest full length headers with 1.75" diameter primaries.
The above combination will easily yield the results you desire, while keeping excellent reliability and driveability. I'd expect a very flat torque curve that exceeds 450 foot pounds at its peak, and is around 3500 RPM wide, with a nice peak HP number well in excess of 425HP. Yes, it is overbuilt with regards to forged components and preperation, but it will make the power you want easily and you will get long life and value for your dollar. I've built this basic combination with varying parts to suit the specific application. The result is always the same, a huge smile on the customers face when he sees the dyno numbers, and an even bigger one when he feels the way the torque shoves him deep into the seat.
If you really are bent on a 383, reduce the intake runner volume to 180cc's, reduce the cam maximum to 218 degrees, and you can use the 880 late model block, with the appropriate Eagle/SRP components. The stroke is the same, so make sure you still use the 6" rod.
I prefer powdercoating to plating, because I like the clean look without chrome and billet. It's durable, affordable, and looks good.
The roller cam design has nothing to do with why Chevy doesn't suggest their crate motors. It's the emissions laws. You could use a crate motor, but then you have ZERO options, you take what they give you. The ZZ3 based engines use the Corvette head and cam from the LT1/LT4 series. You could buy one of them and modify your intake. You can even convert them to the 'hot cam' setups Chevy sells. They really are mostly a mid to late eeghties short block with a forged crank and the later Corvette heads and cam. The warranty will be void when you start tinkering.
