There are some that have two shafts, (= more slop)& others have a single shaft = (preferred.) When I used to go to the junk yards,I used to find more split shaft distributers than the solid one one piece. The split shafts are held together w/a roll pin. Also, there are many w/internal coil in the cap & less external coils,1 or 2 years made that way?
IIRC,1975 ,was the first year on inline 6's for HEI's Also, the plug gap that year was excessive,the following year ,the GM reduced the plug gap to improve passing emmissions easier.
