What I'm trying to figure out is if All the 1972 Distrbutors are all physically the same and maybe different internally(springs or weights) and if they all have same or different vac. adv. units (physically or internally). I have a 1972 400 4bbl auto and am Looking for an original Distributor. Do I need to buy one just for that application or can I buy a 2bbl or a 4spd one and make internal changes if they are different.