460COBRA,
I would suggest investing in leather for covering the dash panel. More expensive than vinyl, but you can stretch it around just about any contour whatsoever on a dash panel. Vinyl is man-made, of course, and if you over-stress it (over stretch it), it might look OK at the time but after a while it may start to separate.
I would use a good contact adhesive and start from the centre of the dash and work out from there.
Use a small roller (1" wide) to make sure there are no lumps of adhesive left that would otherwise show up afterwards.
Maybe try a small section of leather on a scrap piece of aluminium to get the hang of the adhesion process ....practice makes (near) perfect
If you use leather, it will stretch an amazing amount. Get your hands on as much clamping "equipment" as you can for the job ....before you start on the job. That's whether you use leather
or vinyl.
Attached are several pictures that show how compliant the leather can be, how far it can be stretched. Note also the small strip of aluminium I used for clamping and securing the leather at the small end of the glovebox cutout while the adhesive was setting.
Take it slowly, and you won't need luck
Cheers,
Glen