Best I've had a deuce as the GPS said, was 69MPH...It was a very brief spurt...a couple seconds at best, and going down a slight hill(so pretty much no load strain to suck power)...the truck was right at the absolute redline max that would almost send parts flying and the truck had 395's on it...I really was pushing the truck just to see it happen, had a buddy with me that REALLY knows these trucks and he told me to back off as soon as we hit that....we weren't going to be able to hit 70 the motor sounded like it was gonna let go any second.
As stated these things are gear bound like a son of a B....so unless your truck has a gear set put in the axles or it has a true overdrive 5th gear than no matter how great the motor runs....all my trucks have the fdc bypassed and I have even had a 5 ton motor in my truck, they just aren't gonna get to 70 before the motor explodes from revving too high....and BEFORE any body says it is possible, I know anything is possible with enough money thrown at it, but the bottom line is 99.9% of guys on here aren't millionaires with a tractor pull custom built motor in a deuce just so it will go above the geared speed these things will do.
My original plans and still hopeful plans are...turned up multi(or 5 ton) running great so you have good power, put true 5th gear overdrive set in trans, and run 11.00's(like I have in those pics) and then of course brake upgrade....truck should have the gearing and the power to hit 70 but more important be able to comfortable cruise at 60-65 give or take and NOT fall on its face when you happen to hit a little bit of a hill(even if you do have to down shift).