Does 10's was, I think, talking more about the size of the port at the gasket face and general profile on the roof of the exhast port. The heat from a turbo puts a little bit of extra strain on the exhast valve and guide.
The exhast valves need a full valve guide and no back cut valves or minut margin seats. Each item is a heat sink which has been selected by many 300 hour dyno tests at Ford Australia so that the exahst won't spot weld iteslf to the cylinder head when being thrashed. Trust what its there!. The Aussie valves are in fact a little thicker at the guide than US 250's and a little smaller in diameter than the D8 heads from 1978 onwards, so it may be safer under extreme duty.
Any turbo exhast valve needs
1) a good valve seat contact (factory spec or more),
2) large guide support (it is okay to give the guide a 60 degree bullet to it, but never reduce the contact area or the heat won't escape from the valve).
3) a good valve material. (Most early valves were better quality than the 68 onwards Aussie Fords, but way too small. The Diamod grade Yella Terra 1.48's from the YT 1200 head are good, but the No 1 exhast valve can't go past 1.45" or it will impinge on the entre the front water jacket).
4) The port can be remodled only a little or you'll create a sprinkler system (ie hit water). Savage heroics with a grinder won't give you any extra power. Just a clean up is best.
The 2V has 42 mm intake ports, and any turbo more or less ensures you'll have all the horsepower you need!
