I know most people swap for more power but I'm looking for gas mileage. I have a 1999 Chevy 2500 crewcab with the 7.4 454 Vortec engine - 10 mpg - and I'm wondering if anyone has ever swapped down to a Vortec 350. The bolt in stuff doesn't bother me but I'd like to know if the wiring would be a challenge. I've heard that the fuel pumps are different and, of coarse the computers. Anybody ever done this?