How interchangeable are 318 harmonic balancers?

What you guys really don't understand is in Australia CAL imported the engines in batches so our 1971 model car might have a 1969 USA engine in it from the factory. If it has an alloy water pump it is a late engine but if it has a cast iron water pump it is an early engine.
So the timing mark on the left ( Aussie passenger side) is late engine and timing mark on the right (Aussie drivers side) is early engine. I am not sure when Chrysler Australia changed the engines but by VH they were late but the VG model had a lot of hybrid parts in them.
Balancers are easy to get and Rocket industries usually has stocks available in Australia!
P.S. the early engines timing cover did not have a cast in timing mark but had a bolt on timing tag on it!