I believe the top and bottom holes on the left side of the cap match up with the car. So, I was just thinking about drilling the top and bottom holes on the right side into the cap to match the quarter panel.
Maybe on your '68. As you can see, on my '74 (3 bolt) the holes on the car are almost 90ยบ from the cap. The two extra holes in the cap are even further away from the stock holes. There's no overlap that puts the cap at anything close to level with the car. Plus, if you mount the cap into the delrin you can remove the flip top cap from the outside.
Maybe I took the easy way out, but the way I see it all of the holes are covered by the cap regardless. The only way to see the extra holes is from inside the trunk. And even if I took the flip top off later, the extra holes are still covered by the regular cap, and I could always just put a couple extra screw in to plug them.
