Been dealing with that BS since my first '73 back in 1989. Us 71-73 types always were looked down on. Then, people found out about the Boss 351 and all of a sudden, the 71-73s are "cool".
I consider our generation a hybrid, and could get on board with that. The 66-71 Fairlane chassis was quite different underneath. While our cars share the exact same radiator support, front fender aprons and #1 and #2 crossmembers as the 70-71 cars, the rails and the towers back is completely different. The front clip is mated to essentially the same floor pan and rear clip as the 65-70s. I had a 70 Torino GT way back and one of the projects I wanted to complete was to retrofit a 71-73 Saginaw steering box to eliminate the external power assist setup.
As far as weight is concerned, the 69-70 were not that much lighter than 71-72 cars. The 73s added about 80lbs when comparing identical cars, with the bumper and shock absorbers. See the Mach 1 listed weights below.
Some specs below from the dealer facts books. Keep in mind the 70 & 71 are
1970 advertised weight
View attachment 62390
1971 advertised weight
View attachment 62391
1973 advertised weight
View attachment 62392