A few thoughts.
#1 Unless you upgrade to a serpentine/multi-rib belt your alternator, being driven by a 3/8" or 10mm belt (with marginal wrap), should be limited to about 65-70A or so max. With "perfect" belt wrap a 3/8" belt can do 80A for a short time. With minimal belt wrap 60-70A is about the max.. If your regulator can not do this, and only the Xantrex XAR (made by Balmar) could, then the regulator is a major part of the problem.
This article goes into great detail on alternator installation:
Alternator Installation Tips & Tricks
#2 The heat developed in the pulley, due to slippage, is directly transferred into the alternator. If the alternator was not "current limited" this level of heat can be quite a bit more work for the alternator to cool.
#3 Cheap stamped steel pulleys do not do well with high heat and tend to "expand" and loosen the belt further when hot. Billet machined steel pulleys do much better in this regard. 8MR 5/8" ID billet machined pulleys can be found here:
8MR Billet Machined 5/8" ID X 3/8" Belt Pulley
#4 There is something odd about the photo of the external regulation plate? The negative of one brush must ground to the B- stud. This is done
externally because the pictured alternator is an
isolated ground model. If someone grounded that second brush inside the regulation plate, to the frame of the alt, for clearance purposes, it won't work. There is no path to the neg rectifier, if this was done, because it is isolated from the frame. I don't see the second negative brush stud on the regulator conversion plate.....?
#5 What gauge are the B+ (+ alt output) and B- (negative alternator output) wires? These wires should ideally be sized for 2% max voltage drop but 3% can suffice.
#6 You have a 1" foot 8MR with a 2" fit kit installed.. Your engine accepts a 2" foot alternator. Be very careful with that Universal foot mount bracket as they are typically made of cheap machined cast aluminum. A fair number of them have snapped. Make sure there is NO SLOP when you tighten the pivot bolt. If there is any slop a spacer will need to be inserted so the alternator foot is a snug fit..
#7 If buying a Balmar,
not really necessary here, the 120A is our favorite model. This alternator would need a very deep belt load manager setting to run on a 3/8" belt. Buying a 120A now would set you up for better performance down the road, should you decide to go with a serpentine kit.
#8 The difference between the 8MR 105A and the 6-Series 100A will not really be evident as you are limited by the belt and both alternators will happily run at 65-70A (current is limited via
Belt Load Manager).
#9 Yes the dual internal fans of the 6-Series do cool better, and it has a heavier rectifier than the 8MR2401, but unless you have the ability to push either of these alternator to their limits (serpentine kit) there will be little added value going to the 6-Series.
#10 Balmar regulators are programmed at the installer level. There is almost no end to what you can program in the MC-614H. I would however strongly advise at least an alternator temp sensor whether you go with a 6-Series or rebuild the 8MR. A battery temp sensor is also a wise investment.
This alternator covers programming a Balmar Regulator:
Programming a Balmar External Voltage Regulator