iwanta,
I would go with the .82.
I have a T-56 so I have both of those gears.Running a 3.73rear.
The .64 is great on the road when I get into speeding ticket range.Other than that .82 is the gear of choice.
The drop in rpm between your 4th an 5th will have you wishing you had something inbetween or a .82 fifth.
When I get into 6th ,.64,I really have to becareful.If I don't,I find myself at 100-110 mph.Which is just right for the .64.
