Option 2 would be safer of course, but I can definitely vouch for the stock 454/330 taking 425hp all day long. Can only guess 500 would probably be fine as well. Especially if the rpms are kept at a mild level.

I have a genVI 454/330 - as I understand it, all gen 6 are 4 bolt, but rotating assembly is cast on the 330/truck motor. Mine takes a beating, and has for 10+ years now, but is only lightly modified (rect port heads, lightning headers, hotter cam, intake etc) -probably around 425hp or so. The rpms could be the key - mine have always been limited to 5000max. (jetdrive with slightly too tall "A" impeller).