It's easier if there are 2 of you doing this, one to hold the radiator and the other to work the bottom left of the radiator around the gromet. Good luck

 

I had this issue for a few minutes with my 1800R, if it's close to the same, loosen the bolts up, thread the one you are having problems with just a little, then the others. If that does not bring them down, then maybe install the top bolt, then one bottom bolt and then use a set of waterpump pliers and pull the parts together and thread the last bolt in. If its still not seating, you have something out of place, reposition and try again, If it came off, it will go back on. Don't be afraid to lay on the ground.

 

Hah hah, thanks for the suggestions. Just so ya know, I never got the cover completely off, the only screws I took off were the 2 at the top, and those are the 2 I can't get to thread at all. There are 2 metal washer type tubes that go into the radiator holes themselves that seem to be the culprit.