I recently installed a 69 repro dash pad and although it looks good for the difference in price between it and NOS, I do not like it... what I do like is the fact that it has a METAL frame...
If it were for my own car (customer likes the pad and says he can't tell)...
I would peel the new pad off the metal inner structure.
Pull the styrene plastic backer out of the old pad and
Attach the old pad to the new metal inner structure,
This way you have the correct width pad, the correct definition in the stitching details, & etc with the benefit of a Metal frame which will not deteriorate in the UV/heat. (I am much more ANAL than just about any customer)
BTW IF the original pad had a metal frame we wouldn't even be discussing this right now.