Just to clarify if this is what you're thinking (??) Chevy never made a 383 crankshaft. You get a "383" by boring a 350 sbc .030, having a 400 sbc crankshaft machined to fit the 350 block.
By the time you find a GOOD 400 crankshaft and have it machined you could buy a Scat 9000...ready to go.....with money left over. This of course depends on what power level you're aiming for and I hope you're not one of the dreamers that come on here wanting a 2000 hp engine.