Gene,

The PTO idea was just a thought. Since the ZF5 has the PTO take-off I could use a cardan drive which would allow me to mount the entire DC motor, batteries etc. in the box. Power would either flow from the ZF5 to the DC motor or from the DC Motor to the ZF5. Probably not the most efficient way to do it, but if the ZF5 PTO can handle it power wise, maybe this would not be such a bad idea. Would you know where I can get some Cardan PTO take-off equipment for the ZF5? I already put a post on the ZF website.

The ideal place of course would be a DC motor with a shaft that is rated for the full truck Horsepower plus DC Motor power and is spliced between the T.C. and rear axle.
I like your idea of the 4 cylinder diesel (maybe a small VW diesel) with Electric Motor, the only thing is that is quite a change and would get into some pretty big $$$. Ideally if I want to maintain the current truck power output I would need about a 125 to 150 hp diesel minimum and then couple it with a DC motor with enough ummph to get me to 200 hp.