[1G1YY]

Rich, You are correct. It is a 3.07 rear not 3.08...my bad.
And thanks...my truck is still a work in progress but getting close.
My tip is that you use an engine rpm calculator...it will be your friend.
I just did this with your setup....3.07 rear, 28" wheels at 65mph .
With a 3 speed auto your engine will be doing 2459rpm.
T700 4sp auto the engine is spinning at 1721rpm....much nicer, but at a cost in time, effort and bux to install a T700.
The economical way of achieving lower rpm's at highway speed would be to fit taller tyres.
I would not worry about a posi as that will not affect engine speed, just traction to both wheels esp at take off.
Just some food for thought...