Without trying to point any fingers or disparage anyone's otherwise good name, I generally see red lights flashing and hear klaxons blaring when I see someone advertising a 383 SBC with a 'New GM block'. Why not sell it as a 377? No sense boring a a new 4.00" block that obviously doesn't require it. Leave the material there for the next freshen. Trust me, nobody is ever going to feel 6 cubic inches in the seat of their pants.
One of your examples advertised using an aftermarket crank. Our experiences with that particular manufacturer's cranks were they needed to be pulled out of the box and immediately ground .010 to get the journals round. Unless I mis-read something and it was actually advertised as an EGG-le crank.
If I were you, I would look for a reputable, local machine shop. Then you will be able to sit down with the owner/operator and discuss what you want to be done and what has to be done. You didn't describe the crack in your current block, but if it is confined to a cylinder wall you could easily sleeve the block. I can't begin to count the number of race blocks we sleeved through the years. (Remind me to tell you a story about a very prominent Ford Super Stock racer and how he sleeved blocks. Oh wait, he made me promise not to tell... :thumb
If you can, shove a sleeve in there, touch-hone the other seven, touch up the valve job, polish the crank, fit a new set of rings and bearings and you can drive on.
I found there are a couple ways to assemble anything - the cheap way and the right way. And you will get exactly what you pay for.