My doomed 408 build

One thing that comes to mind is that a Blueprint 408 crate engine with their warranty is looking pretty sweet about now.
Your builder sounds like a real dick to me.
He should make it right, lord knows how much you spent there on this build.
If it's a parts defective problem, he could back charge the supplier in yours and his behalf.
To me, the only reason that he wouldn't stand by his product/build is if he screwed up.
That's the thing that truly sucks about some people.
Good luck, i hope it turns out well for you in the long run............