So someone posted the gear ratios over at
http://newtiburon.com/forums/showthread.php?p=2540157
Based on these figures, the I4 has a theoretical top speed of 160mph, and the V6 of 190mph. Now I am not saying they will do these speeds, but the gears in the box are capable of these speeds, with much more HP. I did this using 6500rpm as the rev limit, and for tire diamter I guessed with 245/45/19s (25.7").