no doubt that the wrc cars of today would win easily.
Remember they are pushing around 800nm over a wide range.
and also all the technical aspects are superior.

But the downside is that you dont get that aggressive and insane sound from the big hp engines, and as the wrc cars today has such advanced differentials and suspension they will only loose time if they where supposed to go as sideways as the grp b cars had to.

if i remember right a friend of mine who is co-driver on a 2004 impreza read 0 to 60 in 2.2 seconds on a tarmac event earlier this year.