Hey Brian, check this out:
http://www.rc-monster.com/forum/showthread.php?t=9179
The car is very similar to the GTP in design. Plus it has a two speed! I am only trying to get to 70mph, but I can gear up if needed. You should have fun with it, my 10th scale tamiya that can do 80 is a blast, body choices will be critical, downforce and airflow management will be a big concern.