BLOCK ID DIVE-A2B

This casting ID only tells that the block was cast in 1971 for a lincon engine. The a2b has to do with revisions to the years casting. The problem with identifying the engine size is that both 429 and 460 use the same block and bore. A 469 is just stroked farther than a 429. There may be more markings in the lifter valley. These would give you a better idea of displacement. Otherwise the only way to be sure is to remove a spark plug and check the stroke.