I don't think 6.70's will be a problem with what you listed, more converter will help. I went high 6.50's with less cam, 10.9-1, ported Edelbrocks, 727 with a 9.5" converter that flashed 5000, 4.10 gears and a 325 (28" tall) radial at 3260 pounds. If the heads are decent you could go faster than .50's.
