I have a new glovebox for my 72 z. Do I have to remove the dash to get this thing in? Or can I slip it up from underneath by removing g what looks like the blower for the vent?

 

Removal of the existing glove box retaining screws and door is relatively straightforward and easy. Actual removal of the box itself is very difficult without disconnecting/removing a lot of stuff and you're better off just destroying it to facilitate removal. Installing a stock replacement cardboard box can be very easy if you're willing to accept less than perfect. Here are the steps:
1. Very carefully cut the new box exactly in half longitudinally (front to back).
2. Easily insert left half, making sure box light power wire is in place
3. Easily insert right half
4. Install 4 retaining screws
5. Position box halves to form a straight joining line
6. Cover the joining lines with good quality color matching vinyl 1 or 2 inch wide tape
7. Reinstall door and latch
This method may seem crude but works like a charm and the modification to the box is not at all noticeable, especially with normal stuff kept in the glove box.