what are these bolts for in the drivers side of the trunk

If they're on the side I'd guess they hold the antenna bracket. Hard to tell from your picture. Maybe post one a little farther out?

I looked at my '77 and it looks like they hold a heat sheild or maybe an exhaust bracket?

THere are nuts welded to the bottom the floor pan. Bolts go thru into the nuts.  I dont see any bracket, strange.