Had a '67 with a 289 4bbl. Think that a 390 will swap in with out having to go with as excessive mods as that 460 swap. Them big blocks are WIDE! Got a 351 cleveland in my comet now ( similar on engine compartment size and block width) and the worst thing about it is bolting up the headers. Busted lots of Knuckles. Manifolds would be easy, or use a short header and bolt the on before droppin it in. Should fit with-out any trouble that a self respecting back-yard mechanic can't handle. Good luck; that thing will be a bow-tie thumper when its dun!