RPM at 70MPH

That's the weird thing about these hemi's. You can run them at rpm's that would make you cringe if it were a 440, but with the hemi it seems like its no big deal.

Just for another reference, at 70 mph my 5.7L backed by a T56, 3.91's, and 31" tires runs around 3000 rpm in 4th, and drops to 2200 in 5th, and 6th is mostly unuseable below 80mph because the rpms are just too low.

I like my 3.91's, but with my first gear ratio they are on the ragged edge of streetable for my taste (can be jerky if you dont ease on and off the throttle). Your transmission has a first gear that is not quite a steep (2.45 yours vs 2.66 mine) so that would be helpful in your case. If you think 3.91's might be too much gear and you need to buy a new gear set you might want to consider 3.73's if you can find them.