Turbo small block

SirDan said
I feel like if the new hemi block can handle 600 hp that might be your best bet though. I mean its already got sensors for fuel injection so your halfway there for efi. Id bet the overall engine design is better as well.

As do Magnums for a much lower pricetag. Here's a vote for the 318 Magnum as a basis.

Typically the power's not an issue so much as the tuning and condition. Small issues have big consequences- but that's true of big power in general.