I also have the over-the-glove box set-up. Was kind of a PITA, since there is not enough room for the tails of the autolite gages I used. Other brands (especially electrics) may fit better. One thing I added later, but you should do first, is install angle rings. They are cheap, give a little more clearance, and improve the view from the driver's seat. But that will require a little more machining (dremel) on the plate to make them fit. If I ever get up the gumption to make a template, I would like to get a custom cover plate from BFH.
But, if I was starting over, I would ABSOLUTELY go with a new dash. Less clutter, better view, probably better installation, definitely worth the extra $.