The first question is sort of tough to answer since the majority of older WRXs have been modified to some extent. The best way to figure that one out is to find an older stock car and drive it yourself or find someone who has driven both and ask them. The true 0-60 and quarter mile times for any car are impossible to know for sure. You can calculate numbers based on power, weight, and different "ideal" conditions or you can put 1 or 100 different drivers in the same car and run it over and over again and the numbers will probably be different there too. An average of the numbers you've found is probably going to be your best bet, but like it's been said before, try not to get caught up in the numbers game.