Engine cover

Well I'm in Massachusetts so not to bad for me but... That didn't open to anything

Look in CL New Hampshire and paste in ForSale :Continuous/Butt Hinges Stainless/Aluminum/Steel/Military Door/Boat/Car (Hollis)

Well...let me try to struggle through explaining one thought....

I like using things readily available (and often CHEAP) to find solutions. Things that don't have to mar surfaces whenever possible.

So...my list of things needed:
Resin and matt
Epoxy adhesive
4 small wooden blocks
Steel tube from local home improvement center (maybe 1/4", 3/8" or even 1/2" ID)
2 hitch pins of appropriate OD (Like this www.homedepot.com/p/Everbilt-1-4-in-x-1-3-4-in-Zinc-Plated-Cotter-Less-Hitch-Pin-815578/204276315)

So take the wooden blocks and glue two at the upper corners of the rear gate on the body side. Glue two corresponding blocks onto the back side of the gate at the upper left and right sides.

With hatch secured into the appropriate location, cut short segments of tube that bridge the two wooden blocks that you have already attached. Glue and fiberglass over the tubes and the blocks. Maybe some kitty hair to smooth the transition from the round tubes to the flat blocks and then matt & resin over that?

Then cut each tube in half at the junction of the hatch and sides of the body. This ensures that they are perfectly aligned. Remove hatch and make sure they are fully secured at the hatch and the sides with more glass if appropriate.

Using the removable hitch pins, this creates a new hidden hinge which can easily be removed by pulling the pins and totally removing the hatch for ease of working on the motor. I would also slide a thin nylon washer to keep the hatch centered and moving freely.

On the Bradley I built I used locks like this: www.homedepot.com/p/Prime-Line-5-8-in-Chrome-Drawer-and-Cabinet-Keyed-Cam-Lock-U-9941/100173693 to lock the hatch at the bottom. You can use two (one at each corner) or just one by using two sections of flat material to reach from the left and right sides (I might have pics if you need them)

Is all that confusing?