HAy SAWKING, If your truck will see any street driving might want to go with a carb that has Vacum Secondarys be a little better on Gas.If full on drag truck go with a Mechanical- Secondary carb. Hay I just made a Funny like your Gas milage is for Crap to begain with. 450 to500 HP ,you probably run 44" super swampers 4:11's front and Back Gear good luck Man.we run Sunowco 110 octane at $5.00 a gallon in a 5 gallon fuel cell,get 3 passes befor toping off.Any way just some food for thought on the Carb thing. Remember;IT'S BETTER TO BURN OUT THAN TO FADE AWAY!BBL-CHEVY ALL THE WAY.