I have the same issue with my hood. I contacted Allon Whyte about a new hood and asked if they could reuse the glass window but they said they had tried in the past but it never worked and always had to be replaced with plastic which I didn't want.
I also contacted a local trimmer who deals with vintage cars and he said the original hoods had always been tight and it was shrinkage over the years causing the gaps. He did say he could improve it without replacing the entire hood so I intend getting that done after all the other work is complete.
