I was interested in the trans as well, so I asked and here is the info I received in an hour or so.
I was asking about the differances between the TKO and RS.
"The RS is based on the Borg-Warner T45 that was produced from 1996-2001. It is basically a 5 speed version of the T56 6 speed and will handle higher rpm shifts better than the TKO. They are equal as far as strength goes. Fit is a big difference between the two at this time.
The TKO will have the proper shifter position and not require any modifications to the torsion bar crossmember. Currently, the RS is not engineered for fitment into an E body but will be in about a year. The shifter position would be centered in the tunnel rather than be offset to the side and will be farther forward by about 5". The center section of the torsion bar crossmember would need to be removed in the tunnel as well.
The close ratio box will have ratios of 2.80 1.99 1.33 1.00 .67 o/d.
Hopefully this clears things up a bit."
Hello Keisler, welcome to the site, I have your TKO 600 just itching to get in my Challenger,
Just a bit hung up waiting for the oil pan set up from Milodon so i can get the egine in and then trans mounted.