CAT 3406e Head Question

I have a '99 475 Cat 3406e that suffered a cracked head last season. The head that was put on was sourced using the engine serial #, which is a 1LW. My local Cat dealer gives me a 1539653 head gasket part #, which indicates an early block and therefore an early head, which is what was put on. I've had nothing but problems since, all being with oil consumption and coolant contamination. I've removed the head, and it appears that there are fairly obvious indicators that my block is in fact a later casting, and should get the later head, and head gasket part #2245122. The garage that originally did the job has long since scrapped the old head, so I can't verify this. Is it possible that Cat's recommended part is incorrect?? The most obvious indicator that concerns me is the rear oil return casting. Early motors have a larger return port, measuring 1 3/8 inches, where nine measures just 2cm. This measurement is consistent with later blocks and the later floating-seal head gasket. Anybody have any thoughts here?