I am considering a Blueprint 383. They specify an 8" 400 balancer and a late model 350 flywheel will be required. My concern is how well balanced it will be with aftermarket parts, not used during balancing. I know they build a lot of these, so maybe it should not be a concern.
From Blueprint engines, request a bob weight card if possible.
As for the balancer and flywheel, purchase good stuff, not the china brand.
Sounds like you already purchased this motor? I would get it running asap as I have heard of many complaints that were let go and the warranty went out.
Even better, round up the parts you need and take them to a shop that does engine balancing. That way you know what is happening.
As for the 9000 series cast crank, I have heard good stuff behind it. Its not a forged crank but it will be good for under 7k rpm.
You need to mock this stuff up before you go the balance shop. Make sure your piston bottom balance pads clear the crank throw.
Remember, the 400 balancer is what keeps this motor in balance.
What was said about the flywheel interchange is correct. Late model one piece cranks and early model cranks hubs have a different id.
As mentioned , do a search on the company, issues are out there on this site.