I sure others will disagree with this.First off,292s are not known for getting good gas mileage.Also that 4:10 rear end will never get you good gas mileage either.The rearend might be ok for racing or hauling hay,but you need to get something with a better ratio for highway driving.You could use a 3 spd.with OD,or a Saginaw 4 spd.with OD and keep the rearend you have.I think the T5 5spd.transmission is too light duty for your heavy truck.You might get away it for awhile,but sooner or later you are gonna abuse it and then it's gonna break.Myself i would put in a 4 spd.Saginaw with a different rearend. Overdrive transmissions have gotten very popular recently.I work in a wrecking yard and have been watching other yards selling alot of them lately.
EvilDr235