Denso's, while a bit better than Mopar alternators, just don't put out a lot of amps down low in the rpm range.
I ended up using an AC-Delco CS 144 for that very reason. It effortlessly runs all my add-on electrical accessories with the engine idling at 800rpm; Halogen headlights, twin Spal high-output fans, large electric fuel pump, MSD, and A/C.
Most people(Moparts members excepted) never even notice it's not a Mopar alternator either, but then again, most people don't notice my car has A/C.
1970 Plymouth 'Cuda #'s 440-6(block in storage)currently 493" 6 pack, Shaker, 5 speed Passon, 4.10's
1968 Plymouth Barracuda Convertible 408 Magnum EFI with 4 speed automatic overdrive, 3800 stall lock-up converter and 4.30's (closest thing to an automatic 5 speed going)
| 
.JPG){kind=link}