How interchangeable are 318 harmonic balancers?

i think the offset hole was about either balance, pulley back on in same position every time, or making sure you didn't use the aircon/power steeirng pulley set, with different offsets on a none aircon or manual steering car.

or it might just be a hangover from aussie 273 production, aint got one so don't know

there will have been method to this madness.... and the intention will have been to avoid people getting into a fix, i don't belive they were trying to confound us all 50 years later....

they gave the aussies the 318 and the hemi 245 at the end of Light A Engine design in 1965/6/7 or whenever that was..
if the aussies saw no need to change it, they didn't change it i.e there will be US produced 318s with offset hole pulleys somewhere. you just had many more years of 318s with and without the offset , and wth offset are probably no longer the norm.