AGM or Lead-Acid?

Typical mopar alternator/voltage regulator output at low rpms especially when cold. They tend to not start charging to that 13.8 to 14.2 until 1000 rpms. I agree that no 2 VR are the same but the output at idle is almost always low because of the design of the alternator. I read there's a Ford cop car alt. that puts out at idle. If you are staying stock then you just need to live with it like so many millions of cars have. AGM do not like overcharging and need a different charger. Your trickle charger may not be functioning unless it's designed for AGM.
I recently saw an adjustable VR here. That may be the way to go or the constant output 14.1 V race only unit. I have 1 but have never used it on a street car. If you fix your max voltage output you can run an AGM. If not, acid/lead. Good luck and check your grounds!