A little late on the reply...
The speedo is in MPH, yes? Mine only goes to 85 MPH and this pic shows 120 MPH (?!)
I need one of those since my truck (some modifications) easily goes past 85, like very easily. I'm guessing it is capable of 100 - and being optimistic - 105 MPH.
Did you manage to install your cluster?
You probably already know that there is a console on some of these trux that has the mounts for the OP and ammeter gauges. There is a tab welded to the floor under the floor mat/carpet that you screw the console to. It also bolts under the dash lip. Its an easy install.