It'll be a CVH engine, Neil. You can get a complete top-end gasket set from Burton Power for a touch over 20 quid, just check whether his engine is Carb or Injection. If he really needs only the exhaust gasket it's just under 3 quid and it's the same for carb or injection engines.
For any Ford engine, Burton are excellent, I ahev used them loads of times and have always been happy.
