Ha, I was waiting for the old versus new debate to start!
I think he was running slicks, sure I got a picture of the car in the paddock so I can check that later. There was a write up on that car (in it's current guise) published a year or so ago (in Octane). I'll have to check but I am pretty sure a lot of it's underpinnings were pretty modern (I am 99% sure it's running modern suspension).
Sure the magazine article was talking about well in excess of 600 BHP in that car, so I think the torque levels may well be equal to (or even greater than) a modern Supercar.
I think it's a tough one to call. Yeah, an restricted Group B car stuffed with modern tech is likely quicker than a current car, but when it drastically deviates from it's original specification can you really consider it an "old" Group B car? And if you remove the restriction from the new car that will surely be faster again. A direct comparison of period cars would be interesting, though I wonder how many (if any) of those there are in use.