Speedcal?
 

Alright, I know I'm gonna take some heat for this one, but I just bought a set of the 99-04 Saleen gauges that go up to 200MPH. I did it mostly as just something to set my GT apart from the millions of others out there, and also because so many people have started doing Mach 1 gauge swaps (what I originally wanted to do). So whatever, they're rare and they're better than your average Mac white face gauges.

Can I use a Speedcal to make them accurate? Obviously they'll be way off if I don't do something.

I think once you swap the board's out everything should be fine but i'm not positive.

You may be able to just move the needles to the correct places. (It will only be accurate if the amount of space between the speed increments are the same. Call the manufacturer and see what they reccommend.

If you have the whole cluster I'm pretty sure you need to have a dealer setup the cluster to work with the care because of the PATS system is tied into the cluster