15 years with the wrong belt routing

When I went from a 318 to a 440 in my Charger in 2001, I had to learn the proper belt and pulley arrangements. My donor engine was from a 77 or 78 New Yorker with a smog pump and A/C so that arrangement wasn't going to work.
I looked at cars at car shows to see what was right and was surprised to see many different setups, some sensible, others hacked and poorly aligned.
If you're not interested in factory correctness, that is fine. If you're able to get the pulleys to line up and if belt tension is easily adjusted, that is okay too. The one major problem could come when you lose a belt out on the road. Trying to find a matching belt for a non stock arrangement is extremely difficult. Going to a store trying to buy a belt for a setup that isn't listed in any book will be impossible.
Old belts stretch so even if you find your belt laying on the pavement, it may be hard to match up in the store.