Looking to builds a stockish 5.2/318 for a DD. If I use a 5.2 magnum, it will use the stock roller cam. aftermarket intake and a small Edelbrock Thunder carb, and elecrtonic DIST. cast iron exhaust manifolds. Or should I use a LA 318 (which I have 1986 truck engine) possibly small summit cam, 4 barrel intake, small AVS carb, electronic DIST, and cat iron exhaust manifolds. Will have dual exhaust , and have a 42RH /A500 with stock converter. Rear gearing possibly 3.23. So which combo should provide the better gas mileage ? I got the 318 for free...so I can walk away from it..if I choose to.