IMO, If your swapping due to 35's keep in mind trucks with 3.92 rears have the same size tires as those with 3.21 so If you going to Over size your tires I would be looking at 4.10's to 4.56's. 3.92 to 35 inch tire is exactly if not worse than what you have now.
I have the 8speed with 3.21 and love it.
Dont let the trucks computer and governing trick you into thinking its sluggish. Its controled to perform safely and efficiantly. Try shutting off traction control and manualy shift. You will see the hidden truths to your sluggish feeling.
I Love that Ram took a lot of the fun out of it For me I have everything I need and 19 mpg average.