Swapping in a hemi 5.7

problems with the 6.1? i havent heard. theyll fix it im sure. i wont be ready for any drivetrain item for a few years, which gives the after market guys plenty of time to come up with goodies for the hemi.
has anyone seen any track times for an old car with the new hemi in it? i was thinking that if a 4160lb 300c can get 14s with the 5.7 and 13s with the 6.1 a lil 64 dart like mine should at least drop a second off those times....maybe?
what rearend would you guys recommend. ive read the 8 3/4 is good for 450 horsies, and that anything greater is in need of the dana. any truth to this? thanks