the only zetec I know of is a cosworth made ford cast iron bottom engine for the UK market and unfortunately is not 70kg but over 120kg in fact its almost a 4age in weight.

My old bare unopened suzuki g16b was 52kgs with no ancillaries but inc waterpump
belt and some other mounts including oil. It managed 126hp ate with mild cam regrind, some headers and r1 bike carbs but now makes 132hp with 11:1 comp and sits in a sand rail in Port Fairy. The current owner is going to try and get the speedway midget head that was ported with bigger valves, titanium retainers and quality springs which revved to 11,000rpm using G10B bottom end at 1070cc and 59mm stroke crank, that made 196hp at 10,500rpm as raced by Dynomite performance.
The g16b engine also holds a world record for highest altitude run vehicle using a supercharger to help it in the Andes mountains with very thin atmosphere.

The lightest Nissan L4 engine is the MA10ET found in old march turbo and some exotic
race cars called the zaurus by nismo, they made 80-110hp and weighed 68kg dressed.

edit: correction the lightest nissan engine ever made as a 360cc v twin for the feather