Are you absolutely sure you have the SOHC engine? It's been about 20 years since I have owned a 4.0 OHV engine, but it looks to me like that's what you have. The camshafts on the Single OverHead Cam engine are on top of each bank of the engine, below the valve/cam cover, and that's why the sensor is usually right behind the oil filler cap on those engines.
The OverHeadValve engine has the camshaft down near the middle of the block, so it would make sense that the camshaft sensor on those is going to be deeper/harder to get to. Unfortunately I do not have a manual nearby at the moment to check for sure, but that's going to be my guess for now.
All of the 4.0 SOHC engines I have seen actually say 4.0 SOHC somewhere on top. You can double check the engine type by looking at your vehicle's VIN number. If I remember correctly, it's the 8th digit that tells what engine was installed, but I cannot remember which letter denotes which engine. I'm sure that information is available on here somewhere though!