'72-'80 vs '71-back 904 converter differences

All 904 converters from 1968 on all have the same size hub, and the same size pilot for the crankshaft. The pilot measures 1.810" 1960 to 1967 have the smaller 1.550" pilot. The hub on the 1960-1967 is the same size as the ones from 1968-on. So to answer your question there is no difference between a 1971 and a 1972 converter from those two areas. Converter balance and stalls do change, depending upon the year and the engine. The lockup converter hubs are the same ones used on all 904s and the pilot size remains at 1.810". From my catalog, even the A500 series of converters have the large pilot and use the same pump bushing as a 904.
You say the Ebay converter was a rebuilt unit. Who was the rebuilder and do you have a part number for it?
One of the builders on this forum should be able to help you with the noise.
Hope this helps.