suped up 6

Boring out the slant doesn't have huge benefits. Even if you over bore it .080 you've only gained 15 or so cubes. Wiesco is offering some new pistons for the slant, but probably won't fit your needs vs. cost.
The four barrel is probably a little much from the sounds of what your looking for. The super six (two barrel) will most likely fit your needs if your looking for a little more spunk with bolt-ons.
If your going to be rebuilding the whole engine, I would recommend a few other things. State your goals so you won't be disappointed later. Research ENGRBLDR oversized valves on E-bay. The Erson cam group buy. These last two would have major benefits compared to an unneeded overbore. If you need to clean up the bores, just take out that much. Good luck!