I wish to follow the technology of the diesel / electric locomotive, as I have a 1983 Isuzu P/U with a 58hp, 4 cyl diesel engine, that I would like to have power one of my 10kw generator heads, with a 120v or 240v electric motor powering my rear axle.
As already mentioned, if your generator can only produce 10 kW, then you can't use more than 10 kW of the engine's possible 43 kW output. More importantly, in this configuration with no battery, 10 kW of generator means no more than 10 kW to the motor which drives the rear axle, which is okay for a golf cart and far too little for even a small pickup truck.
So, to just maintain the original performance you need at least a 43 kW generator, and at least a 43 kW motor, and appropriate electronics between them.
My intention is to remove the 5-speed manual transmission and put one of my 10kw generator heads in its place, then idle the engine at the RPM necessary to achieve 60Hz...
What do you mean by "idle"? I actually means to run without producing any useful power, but what you want to do is run to produce exactly the power needed by the vehicle - that's not "idle".
If using the AC output directly from a generator the engine speed does directly determine the power frequency; however, there is no need - or even any reason - to produce electrical power 60 Hz, and there is no reason for that speed (3600 RPM for 2-pole generator, 1800 RPM for a 4-pole generator, etc) to be appropriate for the engine.
... and direct-wire the A/C 120 or 240V drive motor to the generator head to supply power to the motor.
A motor supplied with power at a fixed frequency can only run at a fixed speed; obviously that doesn't work for driving a vehicle, which must vary in speed. The AC power can supply a motor controller (called a VFD for "variable frequency drive" when supplied with AC power) to run the motor. If using a VFD, there's no need for the power from the generator to be at a fixed frequency.
You might want to start with the Wikipedia page for Diesel locomotive, Diesel–electric section
, for a description of what is actually involved. You might note that typically the power from the generator to the motor controller is DC. Also, locomotives change engine speed with changes in the power requested by the operator's control actions (moving the "throttle" lever), rather than running at constant speed.
It doesn't make sense to me to spends thousands of dollars on batteries, along with adding the extra weight, then having to recharge the batteries, when I already have a complete power source.
Without a battery, the entire system just replaces the transmission with an electro-mechanical transmission system which is continuously variable (which is nice) but much less efficient than any conventional automotive transmission... and that doesn't make much sense.