Should I leave it Stock?

if you are strictly trying to sell it eventually, the argument can be made that you will make the most money back by keeping it as stock as possible. If you plan on keeping it forever then tear it up until it makes you smile. Either way sounds like what you want are all bolt on parts so if you keep the original parts and store them correctly, you can always "go back to stock" in the future
273's are fun, but there is no replacement for displacement, it all depends on how much you are willing to spend