Can anyone advise what would be the optimal rpm range for a 3005 cmc 617.952 Diesel Engine?

I have recently purchased a Mercedes Sel with this type of engine installed and it seems that all my front traction, gas-driving skills had become useless on this car. Most of the time I have to floor it to get this 2 ton beast rolling.. this rising another question - should I push the pedal all the way down quickly or gradually to let the engine pick it up more easily?