Stock 360 crank is good to what HP?

All depends on the machining of the block and crank and weight of the parts. If it's blueprinted, and internally balanced, it can take more abuse than something that wasn't. In a truck I'd be more concerned with towing and torque production. My truck doesnt rev over 4500 if I'm being rough, and not over 3200 driving normally. I'm fairly sure if you stay in the "500/500" limits you'd be fine.