No difference there either. Maybe the bowed springs confused you. The rear springs from the first year of the 144 to 1972 are double pig tailed, and if you bolt one end down solid, you will have a heap of trouble getting the other end to bolt up. 1973 has a single pig tail spring with the pig tail bolted to the chassis & the open end ridding on a funky cup that is bolted to the trailing. 1974+ has similar springs, but upside down, the pig tail bolts to the trailing arm & the big cup bolts to the frame. I use the '74+ style springs.

Springs themselves: front 144 springs are all the same, but there is at least four different stock spring rates in both types of rear springs. Stock & optional heavy duty 142/144 springs & stock & optional heavy duty 145 springs.