and the verdict is.............. its a 450. the casting codes are all "D", 1958. and the engine is a C281, not the C264 found in the super M and the 400.
the engine is what i expected. it spun #4 rod bearing and marked up the crank. the PO got it that far apart and realized he was not going to get away with bearings only, and lost interest. broken cast oil control rings on 2 and 4, so far, but it doesn't matter. it needs head work, a sleeve and piston kit, crank grind, and bearings.
or it would make someone a good puller, if they wanted to rework it that way. i wont get to it for a while in any event, other projects