Done this , been here :) only I was running a Novak 4.5. I only managed right over 70,then it was just to uncontrollable on foams.It would start drifting and correcting would make it go haywire. I did not run lead up front,I added a little wing to the bumper.It had no trouble keeping the front down.But it was very unstable. Good luck with this,I always thought it had 80 in it.For the diff you could try this http://cgi.ebay.com/ws/eBayISAPI.dll...%3D4%26ps%3D42 then use Jato shafts and your about as strong as it gets.