I have a richmond/Nash 5 speed in my 442 with 2.75 rear gears. WIth the deep 1st gear, it works out very nice. I never wished it had another gear. It is kind of a clunky shifting thing, though.

The 6 speed in my hot rod is a t56 magnum 6 speed with 2 overdrives. The big cammed Hemi dosen't like to cruise under 2300 rpm. With 30" tires and 4.57 rear gears, I can't get it into 6th until 70 mph. 5 gears would be enuff.