For all those with the original style paper/cardboard glove box insert (left image) in their 240z, I found a cheap and easy way to upgrade to a plastic insert from a later 280z (right image). I picked my used 280z insert up for $10 on ebay a while back.
Here is the picture of what I started with. A huge cut in the back of my cardboard insert from the prior owner. Its only gotten bigger since I've owned the car
The finished product is much nicer than what I had in there originally. I did need to mount the glove box door first and then slide the new insert in. I also put screws into these front holes to hold it better. I probably could have trimmed down the side tabs as well and use the original holes, but this seemed like a much more secure way of mounting the insert. I will probably look to finish the bottom edge better and possibly heat the plastic to shape it better.