Hello there everyone. New to the site and hoping to get some help. I have a 1965 mustang coupe factory inline 6. The engine is beyond repair (hole in the cylinder wall). I have a '69 donor car that I have taken the 8" rear and going to rebuild it with 3.55 gears, the front spindles (V8), T5 transmission, and the springs. I want to have good fuel economy but still have some power when needed for merging or passing. So my question is should I put a built up inline 6 in it out of a '66 mustang or should I use the 351 block I have out of an '88 bronco and just build it stock? What would be my best option?