Man at your age I do not want to discurage you in your indevor. What you should do is price long blocks, junk yards, news paper adds, trading times, what ever. Then do the same with short blocks. When you buy a long block to rebuild you never know what if anything you'll be able to reuse. Most of the time it depends on what you intend to use the engine for. That said maybe you'd be better off buying a new short block and build from there. There are to many posibilities here for a yes no answer.I think you could buy a long block and take it apart and see what makes it tick. Most of all decide what your building it for. Pulling stumps or driving down the highway with good gas milage.