I just had to do it. I "joined" the front and rear suspension, to check ground clearance, driveshaft position, wheel alignment, steering angle and stuff like that. I'm pretty pleased with the result so far. Here you can see what is built so far.
Considering the huge wheels and the big scale it seems that the ground clearence is quite small, I am refering to the lowest point of suspensions. It is hard to perceive the true clearence from the pictures though. I know that the challenger is one of those low riding street cars but still it looks to close to the ground, have you considered the weight of the chassis and the ground clearence when the suspension contracts?
The steering angles look good, but I beleive that they should be tested with the real wheel-base distance to know for sure, I understand this is just to check if it roughly fits.
Ground clearance is 3 studs like it is now, and 1 stud when fully compresed. I did take the weight into account, but the suspension can be adjusted 1 stud higher on both axles if need be :)
I tested the steering with the real wheel base too. Works fine.
3 studs is enough for that vehicle, it seemed less from the pictures, I guess I still cannot perceive the actuall size of the wheels, they are huge!