You're welcome to come restore my stock motor if you want.
Problems: burns oil, fouls plugs (some with hard deposits, some oily black), #1 cylinder sometimes works and sometimes doesn't (I think the exhaust valve is stuck full open), sometimes really fun top end noises, drips, seeps, leaks, and sprays oil from about 30 places, distributer advance mechanism is shot, exhaust manifold has cracks you can stick credit cards through (two at a time, even), needs plugs every 3K miles or so, could use another carb rebuild, fuel pump is iffy,... and, even if all that is fixed, it'll still have only half the hp needed to merge onto the interstate without ing people off.
While I'm staying with my stock motor for now, I can certainly see why people swap them out!
--Randy