Engine mismatch mess
 

I'm sure if I searched for hours I could probably find all the answers to this, but it almost seems like a mess enough to start a chat on it.

I have a 2001 XJ, few years ago we hit a dear and overheated the motor killing the head and damaging the block. I got a used motor from a donor. The donor was a 1997 WJ, and was told the motor was a 1997 Jasper rebuild. Having random issues with the motor and leaks from everywhere, so decided to get a gasket set, pull the motor, clean everything, new gaskets and go from there. Open to machining the block, pistons, and ect, doesn't bother me. Now the complication. Checked the casting number on the right side of the block = 53008405. Searching makes that a 1991-1995, interesting. Called the dealer to verify, he advised to look on the left side for a machined surface for more information. 106MX12 what I found, digging translates that to a 4.0L MAI cast in June 12, 1991.

I have adapted the engine to the DIS ignition w/no problems and it works fine. I have a 2001 XJ intake on it, and know when I changed out the intake 2 years ago, it was broken, I used a 1997 gasket thinking match the block adapt the exhaust and intake manifolds. Water pump is a 1997 part, looking like no differences across the span of years. Rest of bolt ons are 2001.

So re-ordering gasket sets and getting one for a 1991 now, heres the million dollar question. What else do I need to switch out to make a 1991 motor work with a 2001 XJ. So far all I can tell for sure is just the Gasket set, and maybe spark plugs.

Thoughts? Thanks in advance.

Which head does it have?

Sorry for slow response. Between work and cold as hell out. Head 7120, so matches the year range of the block.