1996 4.0l. bought it with a blown head gasket. pulled it apart like a dream and found the break between 2 and 3. coolant jacket easily leaked into cylinder. hopeful, i continued onward excited that it was turning out to be just a head gasket. so i sent the head off to the machine shop to get a valve job and check over. low and behold a three days later i get a call. " theres an internal crack no good.'' this pissed me off because i personally went up to the tech and said please check for a crack before you start valve work. which he obviously ignored because he said he was half way through when he found it. anyway the just of the story is that the service writer told me that the 96 head was non interchangeable. or the casting # 0630 is not interchangeable with any other model years. this makes sense to me seeing as how many changes they were making to the 4.0 when obd ll was coming new but anyway. does anybody know any more or am i just going to have to search the u.s. for the same head. ive called all the machine and junkyard shops around town and the best deal i got was 368 bucks for a reman. one machine shop said there were interchangeable casting numbers but he didnt really sound convincing in knowledge. please help, or critique.