I think the back sitting to high is a very very common problem with hoods. my 66 was like that and I have seen many classics like that. Are you sure that your hinges are closing all the way in the back and that your hood isnt hitting anything?
Check for clearences. Make sure you have the hood hinges shoved all the way down. And as Krash Kendall stated - older hood hinges don't have the pull they once had.
My original hinges are "stretched" after shutting the hood with a socket on the frame rail. Amazingly, the hood did not bend. This goes to show how weak the originals are after all of these years. Worse yet, I have heard several people here say the repros are even weaker.
My '68's hinges are also too high at the rear. I looked and they are adjusted all the way down. Pushing on the back of the hood makes them settle, but they just go back where they were if I open it.
A buddy of mine told me to loosen up the bolts to the fender and push up on the open hood.... while applying upward pressure on the front of the hood tighten up the fender bolts. Supposedly that worked for him on the same problem..... If it works let us know... lol
I agree with blk about pushing upward on the hood after loosening the bolts that connect the inner side of the hinges to the fenders. I was told by a body specialest to do this and after about 5 trys you should get it perfectly aligned. Also its located in the chiltons book.