I'm considering building a 300 for my 78 half ton. My dads got one in a 93 and I love it. Gets 18mpg city highway up hill down hill whatever. It's efi bein a 93. So if I build one I wanna do it for longevity and low rpm torque. My question is how much torque and gas mileage can I squeeze out of it. Plans are: 8.7-1 cr hydraulic roller cam (if they make a roller retrofit kit for these) roller rockers, long tube header, p&p head, 3 angle valve job, speed pro hyperuetic pistons, (yes Iknow I spelt that wrong), mad 6a, dui distributor, ditch the flex fan for an electricity one, either an iffy 4bbl intake or a home fabbed tubular one, and a 4 barrel carb.So power potential with this? I figure if I can run all roller cam and rockers It should help it last a long time. What's a realistick mpg to shoot for? 78 half ton short bed 4x4. Will run a np435 and ranger torque splitter I think. 3.73 gears and a 31" tire.