I'm sure the 8V box will have much lower ratios. From memory, the Mk2 8V had a top speed of about 115mph at getting towards 6000rpm in 5th. The Mk3 16V had a top speed of 135ish mph at just over 6000rpm.
Your car would have been a flyer with the 8V box, but would run out of revs at big speeds. The ABF box will give you the opposite results.