Well after the "cracked mains/aluminum cap" debate.
I tore down a core I`ve had for a LONG time,turns out its a 4006630 THICK WEB block.

So supposedly this a "good" RB block. Caps were nice and tight no obvious cap walk.
So IF it checks out crack free this is a good thing.

So now build options:
3.75stroke 440 11.75cr. 6,700 max trap RPM.4.88 gear cheapest
4.25 stroke 7.1 rod 10.5cr 6,400 trap 4.56 gear
4.15 stroke 6.76 rod 10.5 cr------------

I have the BCR caps,,,, necessary?

I have also found 2 400 cores local for 200 bucks each.
That is an potion too,but would require more cash for intake,push rods ,dist etc...