If you can afford a new 340 Resto block or an older X-block style race block, buy one!

Lots of good Choices on cranks, I like Scat or Callies, but K-1 and some others are good as well. With all of the good/reasonably priced stroker cranks out there now, I'd probably go for a 4.25 stroke just because you can, not so much because you need it.

If you have extra money for anything put it in the heads, again, lots of choices, just depends on budget, I'd lean towards aluminum but good iron heads now too and with some porting can make monster power.