First I mounted a bolt from underneath, through the hinge and into the nut welded into the bracket on the left and right side. Note that you have to remove the battery cover to get enough room to get a socket wrench underneath to tighten up the bolt. I wrapped my wrench with several layers of electrical tape so I wouldn't get zapped by touching a battery terminal. To avoid rattles and scratching due to paint-on-paint, I put a small piece of 1/8" rubber between the brackets.
Richard Rodriguez, I used neodymium magnets from K&J Magnetics to hold the cover in place, since the spring bar and latch assembly is long gone. These magnets are very strong, to the point where they can hurt your finger if it gets between two magnets snapping together. I used a pan-head bolt through the hole in the magnet, small spacer, large washer, rubber washer, through the mounting bracket, then finishing with a nylock nut underneath. In a bit of a happy accident, I over tightened one of the magnets and broke it in half. I used half a magnet on each side as it fits perfectly into the shape of the corner of the underside of the engine cover. I epoxied a small piece of 1/8" rubber to the underside of the cover to avoid scratches and rattling. There's also a loose captive nut that I epoxied into place.
The cover fits flush with the side trim and looks great. It takes a tug on the handle to raise the cover, just like I was hoping for, and it snaps down perfectly onto the magnets.