Hello I will help you with your question,
If you use a "tee" you can use the oil pressure sender to run the vehicle information to the PCM and have your gauge in the cab
The Oil sender is located at the left side of the block by the oil cooler/filter
Let me know if you have questions
I thought the sending unit on the 96's was on the back center of the 5.7 below the distributer and behind the intake . I was hoping there was another port easy to get to. Like close to the oil filter are you sure there is one there ?
This is the oil pressure switch you are thinking of it is for the fuel pump and could be used but as you say it is hard to access.
The sender port is next to the oil cooler adapter.and may have a plug or a sender depending on how your truck was setup but you can tap into the oil galley there for your gauge.
I've been looking for a diagram and this is from a 1999 VIN R 5.7 (same VIN as yours) the port is on the flat above the filter in this diagram
Thanks for using JA!!