Hi Craig,
I just looked at the Nissens in my second 300D. It had that same bracket yours did, but the shop cut off the part that was in the way. It looks like a few inches needed to be trimmed off the top, that's it. I wonder what other car this radiator fits, where that bracket is needed? If none, why doesn't Nissen build it correctly in the first place? Crazy. Mine doesn't have the steel inserts in the necks either. I think that's a new-Behr-only feature.
I haven't measured mine yet, but on my first car at least, I think my rad support is pushed back a little. The engine encapsulation panel has to be "flexed" to get the holes to line up. I think I need to yank the support forward about 1/8 to 1/4 inch. I'm thinking of trying to do it with a bottle jack braced against the frame crossmember, if there's a clear path to do that. Otherwise I'll have to come up with something more creative...
Be careful in the future both with parking space curbs and "stoppers", and dips in the road! I'm paranoid about this on both of my 1987 300D's, particularly since both are lowered, which makes it much more susceptible!
The 1984 is stock and appears to have almost as much clearance as a HumVee. :p
Regards,