Originally Posted by carsavvycook
Just the crankshaft and connecting rods if I remember right. The harmonic balancer might be different, along with the flex plate, or flywheel. It is externaly balanced if I remember right.
The crank and pistons need changed. The rods are the same and it is INTERNALLY balanced, not externally. The 410 and 428 are the only externally balnced FE engines.The flywheel and harmonic balancer can be retained.
Just a note regarding a larger engine vs. fuel mileage. A larger engine does not mean that the mileage will drop. Since the amount of work is related to the throttle position, you can have a larger motor that gets better mileage because it isn't working as hard. The amount of throttle required from a 360 to get the same amount of work as a 460 would be considerably more, thus decreasing mileage. Now this is with the same driving technique. It isn't uncommon for people to want to use that extra inches and have their foot in the throttle more to feel the power. This, of course, hurts the mileage. So a larger engine isn't neccesarily going to deliver worse mileage, there are several variables that apply.