[diesel_john]

welcome to the site AmpEater. I have dreamed about doing a project like yours. You are doing great. My 2 cents worth may be not be worth 2 cents.
So ignore me, if your past this point. A direct coupled (shaft to shaft) engine to gen. would be considerably more efficient than belt driven. Is it possible to run the engine at it's most efficient RPM or do you need a certain frequency. A much smaller engine could be programed to shut down after you park at your destination on long trips. When leaving home base, the gen. could be started early on if the trip is to be long. I am a diesel fanatic but diesels are a challenge to isolate. (vibration and sound). Air rides, internal balance shafts, big intake and exhaust mufflers. The smallest single cylinder that will keep the batteries up would be good. I have driven 500 miles without stopping but I would have been safer if I had stopped every couple hours for a stretch. And let my "batteries charge". I would be tempted to try a little tiny, smooth, quiet off the shelf generator first to see how the duty cycles work out. Do not know if any little gensets will burn E85. Direct injected flex fuel engines will compete with diesels. You can quote me on that.
The price of diesel on the road has lost its advantage.
10 % winter to 20 % summer biodiesel blends do burn considerably cleaner in my engine, than straight low sulfur, and no heater. Electricity may or may not be a renewal fuel but B100 argueably is.
Is there any way to run a shaft out the back of the motor or transmission, or differential to direct couple a generator for regen. capability. Or a motor/generator all in one. The big advantage of batteries is the regen. capability. On the transmission, the direct drive gear is the most efficient not fifth. Although the ability to down shift might be great for regen. After your drive train is running, if you add aero modds your not going to need as much power as you think. Again my thoughts are meant only as encouragement.