360 magnum will be the more reliable engine compared to the 383 especially since neither has been rebuilt. You might do a compression test to get an idea of the shape of your 383. All things being equal the 383 will make more power. Not to mention everything on a big block is easy to work on vs the small block. I did a 318 magnum into a 70 coronet, best thing I've ever done for that car. The magnum engines do make an excellent daily driver.