next project...rear plow

Without knowing the power the plow pulls, impossible to recommend. Remember that all this puts TREMENDOUS load on the charging system, not just the alternator, but the wiring as well. You have to re-charge those two big batteries

There is another caveat........the more load you put on a vehicle system, and start to pull it down, the electrical noise caused by both the alternator (ripple at minimum) and the loads (motors and switchgear) goes UP. This can raise hell with the vehicle electronics

You might want to investigate a much larger alternator and direct wiring charging line. similar to an "ammeter bypass" except---there probably is no ammeter, but the point is, get a direct heavy route from alternator to battery.

It MIGHT even be time to consider isolated systems..............Two batteries, one only for the plows, with a separate added alternator