they used some of the ls6 engine in marine use but a brass runner in the intakeand brass block plugs and a lower cr pistons if all black could be merc marine engine 375 hp/454 that would be 7/16 dimp rods steel crank 188 heads.big oil pan with tray .valley tray . hard to say what it is that block was used in a lot of things . i just got done working on 3 of the 289 one 496 .two bolt . and one 4 bolt block427 . and a two bolt 427 .of all the block numbers i see alot of the 289 blocks