So many options out there for engines.... I have an original-to-car 318 in my 71 Swinger, so I'm weighing all small block options at this point. Either keep the 318 and send it to a performance machine shop; find a 360, or find a 340. I'm in the works with a guy and a 340, but i'm torn between that, or rebuilding the car's 318. Would rebuilding the orginal 318 keep more value to the car? Ready, set, go for opinions.