73 to 72 or 71 parts interchange?

i just got a 73 swinger and some of the stuff ive been looking at end at 72 or 71? like a fuel tank and some other lil tidbits. whats the differences between a 72 and a 73? i think the suspension was change cause they went to discs and bigger bolt pattern but im not even sure. just any help would be appreciates.