The ribbing on the side would indicate it's a late 60's block, 67 or later I would guess. Most likely an "over the counter" replacement type 427 side oiler block. The
oil galley screw in plug in the lifter valley also indicates a later 60's block that can run either solid or hydraulic lifters. The early blocks were ONLY solid lifters. The cross bolt mains say side oiler, as do the screw in freeze plugs. Over the counter blocks did not have typical casting dates, like C7AE or whatever. The date code clock like symbol is a bit complex to "read" but you will find it under or near the
oil filter area (I think thats where it is...).
Just a guess now, but I would think the paint marks on the block may well be original factory stuff and indicate the block has never been assembled.
Any single one of the above items may or may not be found on some "ordinary" block, but the presence of all these items on a single block strongly point to a side oiler. The Coup de Grace would the bore measurment, that should nail it! A potentially VERY nice and rare find, me want...
