I don't understand why 80mph should have a bearing on anything to be honest. An engine doesn't care how fast the car is going. It'll still produce it's power in the same manner in every gear through the entire rev range.

I have a 1.6 steel and forged CVH. It's a bit laggy as the turbo is quite big but it'll get to the limiter in 5th before I have even realised what speed it's actually doing. The same turbo on a 2 litre Zetec will be a lot more responsive as the capacity will help in the rev range where the turbo is asleep. The capacity of the engine is pretty irrelevant to maximum power but it does help spool the turbo quicker and it will produce a little more power when it's off boost.

For decent power, either engine will work. For a more responsive engine, the Zetec 16v engine is best. ZVH engines I would avoid to be honest.