It probably is a 79. There was a change in the head and valve cover, the stock 79 valve cover was steel and the stock 83 valve cover was plastic. Heads get swapped but if it has a steel valve cover it's most likely a 79. Also, you can use the 7/16 bolts (if you have them) no problem with a 4.0 head. I bought some spacer/washers for mine, the 4.2 head I replaced had 1/2" holes and no spacers and worked fine with 7/16 bolts also. Two spacers would insure the head is where it needs to be, the head bolts don't care if there is a little space around them. You can redrill the block and use 1/2" bolts but it is a waste of time and money IMO. <img src="/forums/images/graemlins/cheers.gif" alt="" />