looks to me like a 427 block, with 428 heads on it. but i have seen guys crossbolt their 390's too so that doesn't clinch it
the date codes will be cast on the block right above the
oil filter housing.
the casting number will be on the side of the block towards the front. some later blocks will not have a casting number.
take a pic of the passenger side of the block right above the cross bolts.
we can then tell if its a sideoiler or not.
the rear bulkhead may have some things scratched or cast into the block.
good luck on your mission.....