They are numbered 1-2-3-4-5-6 front to back.
Number one spark plug is closest to the radiator.
The spark plug gap for the 1994 Jeep Grand Cherokee 5.2L (318CID V8 is .035".
the 4.0 six in a 90 jeep Cherokee is not a v6 it is an inline 6. the firing order is 153624
I believe you have to buy a whole new coil rail.
It can be done, but it won't be a simple "plug and play" swap.
1998 Jeep Cherokee 2WD 4.0L MFI 6cylThe Spark Plug Gap.035 (In thousandths of an inch)
.034
On the v 8 it is the front driver side cylinder.
.035".
.035
The fill plug is on the center of the rear of the transfer case.
check the spark plug wires and the distributor cap wires