Hey David , sorry I missed this one , it's one of my favorites ! I like that you were able to adjust the front bumper/grille upward to fill that gap , and moving the mirror really improves the look of the dash . I've had to fit tops to bodies like your doing and it's a time consuming task but well worth the effort , looks like you've got it handled.
As for the track looking too narrow . . . I thought the exact same thing when fitting my '60 Dodge . After looking at tons of photos on the web and at some finished models I decided to leave it alone . The finished models look great and none of them appear to have the track widened , check some of Steve's models and you'll see what I mean .