If you are very close and still can't get it, it is possible you mangled the threads in the head and that's why you can't get the bolt started. Just something to be aware of

 

threads are fine..they go in easy without the header on...

 

I got the passenger side on finally. I filed the front two holes to widen then up..however the 2nd bolt won't fit in, and with the primary tube in the way can't really file it much. Is it going to be a huge problem if I leave that bolt off? When I took off my exhaust manifolds, one of the bolts on the drivers side was missing, and I didn't have a leak. Would this cause a tick-tick-tick exhaust leak or can I get away with it?