can I just use the bottom alt to charge back battery and supply power to the sure power witch will then charge both batteries instead of using both alts. or is there a reason to use both alts
I think your mixed up about how its supposed to work. If your truck has stock alts, they are 24v. The 24v alt(s) will charge both batteries at the same time in a series. The battery equalizer is used to supply a stable 12v power source for the 12v systems of the truck. 12v source is also tapped from the front battery.
Depending on your specific need for 24v power will determine if you need one or both 24v alternators. It will also determine if the second solution presented in this thread will work for you. If you dont have the 24v lighting and AC working in your unit, then you most likely dont need both 24v alternators. In which case, you can choose to do 1 24v alt + bat equalizer or 1 24v alt + 1 12v alt.
In either case, study the wiring diagrams so you dont wire it wrong.