i just noticed a post on the fit of repo dash pads.
i'm rebuilding a 70, and of course ther are many cracks and fractures in the plastic backing of the dash pads. my lower left had so many breaks it looked like the car rolled over it.
i work in a dental lab, so i took a long shot. the acrylic that is used to make (and REPAIR) dentures bonds to the plastic pad parts.
here's my technique. clean the broken edges of all dirt and oil, use a drop of super glue to hold the parts in proper alignment. when the glue sets, use a dremel to V out a portion of the fracture line, leaving enough to prevent the two pieces from coming apart. use a Q tip to apply the acrylic bonding agent to the fracture line and beyond to extend the area for reinforcement. the acrylic is a powder-liquid material. mix a small amount (a table spoon or so), let gel for a minute and apply as you would fiberglass except there no mat, it's all resin. you can use a q tip damp, not too wet, with the liquid to smooth the edges and rough spots. it sets in about 15 minutes, but to ensure total bonding to the pad plastic i'd wait an hour. then do the other portiuon of the fracture. the trick is to keep the liquid from evaporating before the stuff sets, so lay a wet tissue over it. you can trim and smooth with your dremel after it sets. it works really well and seems to by as stong as the original plastic. the only problem is the color-it's pink! the acrylic is available in other colors, but i know the pink colored stuff is higher strength than the white or clear.
if you are on good terms with your family dentist, you can get the stuff from him, or a local dental lab.