Do note if you have different tire sizes then stock, you'll get different speedo readings.
I'm pretty sure the 3 is identical to the 6's gov, which is 128 in 4th gear in the MTX's, or 120ish in 5th.
Honestly though, if your going 120, and trying to look at your speedo, or take a photo, your a f$#king dumbass.
Might as well just go ahead and send in your application for a darwin award now, and save everyone else the time.
http://www.darwinawards.com/