I forgot to mention that I already have a 2600 converter for a 4l60e that I planned on using in the truck. Because of this I am leaning towards the 60. Due to cost, I was planning on going with either a very low mileage or local shop rebuild 60. It would at least have a corvette servo, overdrive servo and transgo shift kit. I would like to not have to worry about the trans going out though. How much difference would there be in gas mileage between the 60 & 80?

 

most people lose a tenth in the 1/4 mile, but pick up around 1.5 MPH. IIRC

Not sure of mileage difference?