Erik, if you do go factory crank and all, the KB hyperutetic cast pistons work well, and are lighter.
340 E heads will be needed if the KBR243 pistons are used.
Thats my combo and it will work on pump gas (mid to premium).
but it is kind of old school. That said, if I was to do over, I would go to a 4" internal balance.

good luck, and if you do go factory route, you can PM me for more info.