Man..that's a hard one. I wouldn't do it without drilling..but I don't know if I'd do that to my GT500.
We usually use the A pillar. It's a lot easier. If you do it this way use SOS pillar. It's a factory match perfectly. You can also go in the vent slots as well.
The gauges themselves are fairly simple and straight forward.
Wideband air/fuel is a must and I would only add boost if you plan on adding more boost which I assume that's what you plan on. Oil pressue is a good one. If you get too crazy you you'll want a fuel pressure gauge as well.
Since the Shelby factory gauge only goes to 15 if you add say a smaller pulley that will bring you up to 12 psi but if you add say a 10% OD mine shot up to 17-18 psi so I had no choice but to add a gauge.
Hope this helps some.
