Here is somebody who is converting an F250:
They are using dual warp 9" motors and 40 flooded batteries. I think their plan is to use a Z2K controller as well but you should read it instead of relying on my memory.
Depending on what performance you hope for, the dual 9's would work, or a single 11" or 13" would work too.
Finding a controller might be an issue as Z2k's aren't being manufactured right now. I think logisystems makes a 1000A job, might be your best bet.
With a camper at 60mph, I seriously doubt you will be able to find a way to get more than 20 miles or so worth of range. serious drag in addition to all the weight.
Your "generator" is going to have to be big. best bet, probably a geo metro engine. You are going to have fun building the necessary circuitry to transfer that much power from a generator into the batteries.
Maybe a better bet is to find a 4wd truck, and make the front half a pure EV drive, and the rear half ICE driven, and just run one or the other.
Admittedly I haven't been around this stuff /that/ long but so far I have not seen a homebuilt hybrid that looked practical and actually was significantly more efficient than a gas only version. It's hard to marry such disparate systems and make everything play well together.
Perhaps your "hybrid" should be an EV motorcycle or lightweight NEV class vehicle towed (on a dolly) behind the camper?? Hook up an extra 2KW alternator and inverter to charge the thing while you are driving your camper down the road, and put a few hundred watts of solar on top of the camper to top it off while you are parked. I bet the whole setup could still weigh less than trying to stuff it all into the truck and you have the advantange of minimal customization to any one component of the setup, instead of having to massively modify the truck.