Craig,
That is very similar to the one I designed. I will try to load up one of my scetches. For the hinging mechanism, I am using a trailer spindle which when all said and done will be very similar to your hinge. As for the latching mechanism, I am going to use a stainless steel toggle latch that is rated at 2000lb and is completely adjustable. I am gonig to add provisions for the third brake light to keep it legal, a hi-lift jack, and where the factory bracketry was, I am going to mount an air tank. The bumper portion will be integrated into the frame, and will have cut outs for back up lights recessed into the bumper to keep them from getting all mashed up!
The only thing I have not done is get my exact measurements, That is on the "to do list" for sunday.
Johnny