Ok, I just noticed this today, when I'm driving around, I have good oil pressure, as per my oil guage, but when I stop my guage looks like its low on voltage, it only does this in drive, and not very often, what does this mean?

 

That sounds like your oil pump is going bad. Had a 5.0 that the oil pressure would drop at low rpm like idling in drive with my foot on the brake.
That motor didn't last long after it started this! Lol

 

Mine does the same thing. Been doing it since I bought it last year. My old 77 f100 did the same thing and did it for years even up until I sold it. Never had a problem

 

the gauges in these trucks are pretty much dummy gauges. i wouldn't worry about it if it has movement. you really want to know what it is you need to buy a real oil pressure gauge. same thing with all the other gauges, just buy one of those 3 gauge kits and install it.

 

If it is my pump how would i go about changing it?