Alernator help/question

[BMSJaX]

So my truck has recently become my daily driver due to my 2000 Impala's trans going boooom , been waiting for it... the car is a piece anyways. And with the time change I now drive in the dark halfway home and I have been watching my volt gauge... Idle 14v, Idle w/electric fan 13.5v, Idle w/electric fan AND Hella H3 headlights 12v and if i sit at idle too long I slowly start droping in voltage and my lights start dimming but it i up the rpms over 1000 it goes up to 12.5v and holds. I have a standard 55amp ext/reg alt I am also running a H.E.I. dist. Does this sound like and alt problem? If so will a 65amp alt do the trick or am I gonna have to go with a 100amp alt? Money is kinda tight at the moment and the 100 amp is twice as much as the 65amp... I'd get the 100 amp no questions asked if I had the money to throw into it.

So what do you guys suggest? What alt are you running with what accessories?