A few questions:
1. What engine is in this? The 300 i6, the 302 or the 351W?
2. Is this a new condition?
3. How long have you owned the vehicle?
To determine if you have a real sender or an idiot gauge is quite easy. On the 302 or 351 (don't recall exactly where it is on the 300 I6), on the drivers side of the engine, just above and to the front of the oil filter should be a hex shaped "stick" coming out of the engine with a sensor on the end. If this sensor is large and shaped a bit like a bell with one wire coming off the top, it is a real oil pressure sender. If it is quite small, it is a pressure switch.
If you have a pressure switch it is telling you NOTHING other than you have oil pressure. Which means that any fluctuation you see in the gauge is electronic and not related to the engine in any way, shape or form.
On the other hand, if you have the pressure sender, you do NOT have the idiot gauge and the behaviour you are seeing is NORMAL. A Windsor has a pump with a 65psi relief in it stock, if you are driving it cold, it will generate oil pressure north of 50psi and you may even hit the relief (unlikely). Once warmed up, you are probably down around 25psi hot at idle or in that neighbourhood.
Also, when the pressure senders go bad, erratic behaviour is the result. The one on my Mustang would be really high, then NOTHING, then low, then high then "normal" for a while. Replaced the sender and its behaviour went back to "normal".