mercedes 1979 450 sel 6.9 hp
 

does the australian 1979 6.9 engine develop more horse power than the uk and american spec motors or less.

go to M-100.cc and your questions will be answered. USA had lower compression than rest of world.

All European 450 6,9's had 286 bhp / 550 nm (405 lb ft) @ 3000 rpm.
USA spec cars had 250 bhp and 500 nm (370 lb ft).

Don't know about the cars you got in the land down under, but haven't you always had cars with lots of cylinders and lots of power? :D

Australian cars were smogged, not as much as the US cars but I expect them to have the same or less then Euro cars.