[joedoh]

I have my 48 cab out on my body cart, taking apart my s10 in the unseasonable warmth tomorrow, so I can get you that measurement while I am out there.

really if you have any kind of machinist square (or t square, or anything similar for woodworking or whatever) though you could lay it across the two steering column mount holes under the dash (to get it square on that axis) and then the other axis will point right at the firewall at the spot where the column is centered. you could even clamp a paint stir stick to it so it will TOUCH the firewall in the right spot.

just thinking out loud. check back tomorrow, I will see if I remember to measure for you haha.