All the smog issues aside...
Not sure how many of the 4.2L parts would swap.
You could make an adapter from the intake to a Carter BBD to take care of carburation.
And you still need to full the injector holes so you don't get a vacuum leak (drill/tap/ pipe plug).
Then make linkages to the throttle, and kickdown for the automatic if it's so equipped.
Then there is fuel delivery. Carbs take 6-7 psi max at the fill valve seat. Any more than that and they overfill, so your fuel pump will need to be changed to a 6-7 PSI unit.
Now on to ignition. You will have to get a distributor with either a points setup with vacuum advance (Standard coil), or a reluctor and vacuum advance (Electronic ignition) to make this "old school" (aka up to 85' or so
).
In the end, you will end up with a 4.0L that runs like it's that time of the month.
Best off to trick the old system into doing what you want it to. There are folks running 12's in "Stock" XJ/MJs in NHRA competition, so it can be done; I've witnessed it.
As for the Dad problem
I know the feeling. I had an Uncle like that with radio. If it wasn't tubes, he was confused. You just have to encourage him to keep up with the times if he wants to do much more than add fluids. Even an oil change isn't simple anymore. The new cars you need to reset the oil timer and even the folks at Quicky Lube don't know what to do with that one since it seems like they are all unique to the Make/Model
Good Luck!