Oil Pressure in a 3.3L V6
Aren't those supposed to take 5w-30?
For winter weight, yes. On the engines from the '90's Chrysler usually recommends 5-30 in the winter, with a switch to 10-30 in the summer.
As far as the gauge goes... "L" is low. That's what it means. When it hits the "L" then the oil pressure is low. Sounds obvious, I know. Anything above that is considered normal.
You can always use both the factory gauge and an aftermarket one. The sending unit is pipe thread. It doesn't take much to T one off between the factory unit and the block and run a capillary tube for an aftermarket gauge.
But Tom is right. The sending units on these things like to crap out. After a while they'll develop small holes that will allow oil to seep by making the gauge do all manners of funky things.