Maybe you saw it, but up a few posts I've started a thread on how to make your own cowlboard using floor protector paper and PVA glue (school glue). 4 layers laminated and sealed with polycrylic Minwax water-based finish is tougher and thicker than the original cowlboard. I suppose if you wanted to you could laminate them using fiberglass resin / hardener or maybe something like polyurethane. It might be more messy, though and certainly more costly. I used a glove box I made to duplicate the original about 50 years ago and altered it so as to be shorter, not have the weird sloping part on the right hand side and with a cutout/shroud in the right rear to allow an ac & heat duct. Since it was designed to install from the front, I left it a bit more flexible and added some hanger strap, screws and screw nut things...so I can get it in easier. Are you talking about making a metal one to duplicate the original box? With heaters in place, I think most of those were installed from the front also. There just wasn't always enough room to go in from the back side. I could probably make a pattern for you. I'll attach some pictures...the old one first and the new one second. Around DFW the harder it is to get into your glove box the more damage is going to be done making that happen.
~ Jon 1952 1/2 ton with 1959 235 | T5 with 3.07 rear end