OK I out my rear taillights and bumper on. It has about an inch gap above the bumper to the taillights. I've googled and seen others the same way. So is this correct? Hopefully you can see in the pic
There is a bumper filler that goes in between the body of the car and bumper. It is very tough to find. I just purchased mine a couple of weeks ago from a guy on here.
I don't think that much of a gap is correct. Have you tried adjusting with the brackets? Also, can you weld? It is fairly easy to take up slack like this in bumpers by cutting , adjusting and welding on the bumper brackets. The gap on my rear 69 Cuda bumper was pretty bad, and I cut about an inch from all brackets. Once I welded them up and powder coated them, they looked great, and the bumper fits great. You can do it.