Duratec 4/4........
The zenith of the 4/4 imho.
The narrow body, perfect engine, lightness and nimbleness, availability of parts, all the 'modern' bits but not remotely modern or sensible......!
Perfect.
I'd go with this, or the X-Flow if one wanted to go the whole points and carbs thing.
My 4/4 had a CVH engine originally but It was knackered and in early 2008 I got Kevin Vernon to bung in one of his Ecotec conversions (1800cc Z18XER engine as fitted to the Astra Sri but with a MBE ECU bringing power up to 165bhp).
Since then the engine servicing has been minimal, I've just changed the oil and filter every other year, put in a new set of spark plugs every 5 years, and replaced the timing belt at 10 years. Far less hassle than the CVH and loads more power. I can't see a Durance needing much different, and they're a lot easier to find than a Vernon conversion!