Complex sentence: Engine was frequently a Ford V6 (Essex or Cologne), though one or two had Jaguar XK's; another was built with a four cylinder Leyland Sherpa O series engine and at least one Daimler V8.
Split into simpler sentences: Engine was frequently a Ford V6 Essex (or Cologne), one or two Jaguar XK's. One was built with a four cylinder Leyland Sherpa petrol engine and at least one Daimler V8.