By one very well documented and usually accurate set of formulas you find that a 9000 kg vehicle powered by a real 250 HP will do the standing quarter mile in 26 seconds and be doing 55 MPH at the end.
If the HP were a real 450 the time and speed would be 22 seconds and 66 MPH.
Take that data for what it is worth. It sounds about right.
A Ferret Scout car at its best does 26 sec quarters,, I dont remeber the MPH. And yes somewhere I have pictures
I suspect the thing must have moderate accelaration and speed as both of those are often more handy than all the armour in the world.
Personally If I was having something like that built it would be the most powerfull engine available with bullet prooff glass, tyres and lots of kevlar armour. And probably weigh in under 3 ton. Something strong powerfull with good road manners that can 'run away' is far more usefull than a lumbering tank.
I believe MB make such a thing, probably GM too in the limo range.