Hey Chris, I ran into the same problem and ended up making my own. I was building the AMT 67 Camaro. I started with the kits rear axle. The factory covers have what I would call an eyebrow across the top portion of the cover. I've included a photo of a typical 12 bolt rear cover. I took a strip of plastic and glued it to the axle and filled and sanded it to the correct shape. At the time I just made bolt heads" 12 of them" and added them to the outer edge. There a little big here. I just tried to evenly space them apart according to the photo. I have since found Plastruct hex in really small sizes that I now use to recreate bolt heads. Hope this helps.
I returned to a store in Snellville, my first trip there they had very few kits, left empty handed. Yesterday, they had restocked I guess,and had a great assortment, I bought three more kits Brings my total up to 9 purchased.
I picked up a Belvedere kit from my LHS, the last one they had, got it home and unwrapped it and the body is really warped, twisted. Did yours have this issue. The body is really thin and it seems like it might work after its all together,and glued.