I want to hear what others have experienced, but here is what I have found when having low DCR with a low stall TC (or too high gear with a manual):
- When 'off the curve', you can push the throttle 1/4 of the way and then all the way down and it makes hardly ANY difference; it accelerates slowing at the same pace regardless of throttle positions of 1/4 or 100%. In other words, throttle response is non-existent. Have you ever driven a loaded truck and picked too high a gear, and put the throttle to the floor and the acceleration did not change? It's just like that.
- When you get 'up on the curve', the thing takes off. You end up with a light switch-like behavior: off, then on. If you ever have ridden 2 stroke motorcycles, you will know how this feels: get the RPM too low and the thing just falls on it's face. My overcammed low CR Opel was (seriously) like a light switch. You have more cubes to weight, and not as bad a DCR if in the low 6's but it will still have an off-on character. That on-off character, plus the non-responsive throttle at low RPM's, tends to suck when trying to accelerate out of corners on back roads.
- As far as 0-60 times... I can't say a number with total confidence. But several seconds improvement would not surprise me with the cam change you mention. The guy with a 7.4 DCR and the XE256/262 valve lift of .447"/.462"will be far ahead of the guy with a 6.7 DCR and the .421" lift of the present cam. And with the added lift, the advantage will continue past 60 MPH; the performance will be better past the mid RPM's 'til the heads' flow stall out.