Obviously they all are important, but what would you focus on?

Looking at a 383 street car, ~400hp and under 10:1 c/r with a peak RPM of 6000.

i'm guessing you mean, if you only had the cash to upgrade one, which would it be? then i'm saying pistons.

crank and rods effect strength mostly, pistons do that too, but also effect compression ratio and flame travel and therefore some engine characteristics, more than the others, so pistons should be focused most on.

I would worry the least about the crank. But good rod bolts are very important. You also might as well go with cap screw rods to eliminate any cam contact problems.

You can take a cast crank pretty damn far. I've really never heard of people breaking a crankshaft, but I have personally blown out a few rods in my day.

I think all 3 are important, so I didn't vote. Everything depends on what condition the stock crank and rods are in....

-But you already knew that.....

if i had to build my engine around 1 part it would be camshaft selection myself but, outa those 3 i'd say at your level pistons also.

Stock crank, R&R rods with ARP rod bolts, then stick your money in the slugs if you want to stick your money anywhere in the bottom end. The stock iron will take alot of abuse...been there

in my car the most important parts were compression,cam,stall converter,gears and tire size

You mean there's no choice for machine work? Of the three available, for the application stated, I don't think there is any other choice but pistons.

That's a retarded question. And very broad at that. In terms of durability, the rods take the most abuse. That is, of course, unless the motor is out of tune. Then the pistons will take the abuse of detonation etc. Think about it, you've got a piston traveling up the cylinder, building momentum the whole way. Then all of a sudden the crank tries to change the direction of the rod/piston. All of the momentum now has to change it's direction and move back down the cylinder. Guess what takes all the abuse? Those two tiny little rod bolts. But like I said, if it's detonating, the pistons are going to take a beating as they try to push the crank out the bottom of the block.

To answer your question you should focus the build on the bottom end as a whole. Set out a plan and follow it. If you plan to build an n/a 383 with 10.1:1, do that and don't spray it 6 months down the road. If you want to spray it, build accordingly. And keep it in your budget. If you get yourself stretched too thin and start to cut corners then you're going to end up doing it twice.

I put pistons b/c one piston slap will drive you crazy(ask me how I know) and two with a forged piston, you can't really hurt it with nos or anything.

dialed in is a smart man.

Dialed in has to put what he reads in context:

Since Token has been on for a while and has participated a good amount in the gen tech area instead of the appearance board, one can safely assume he has at least a grasp of the concepts that have been covered countless times. That said, in that context, with the limitations he presented, you can'y make a recommendation? He's not asking what part to blow money to the detriment of the other components, he's asking in a roundabout way which should be at the top of his list. I'd personally rather see machine work at the top.

Right up with machine work I'd vote for cleanliness! Mic, polish, and clean the crank. Shot peen the rods and add some ARP hardware. Then get new forged slugs and go to town! With 'only' 400hp you could probably use hypereutectic pistons as long as you aren't going to spray it.