If you want good fuel economy and power - leave the fuel injection on it.
What are your plans for this truck? Daily driver, rock crawler, desert, etc?
I wouldn't waste the money on a 318. Find a 360 (LA or magnum) and start your build with that. 408 stroker kit, better heads with minor bowl and runner work, Hughes roller cam, Hughes FI intake and programmer. Good for 485-515 Hp and 500 lbs\ft torque depending on the specifics.
One last thing - there is no "rock crusher" its just a NP241