I have a little bit to add. The nomenclature of 100 150 200 250, were not available in the same years. 100, 200, 300 were altogether. Likewise 150,250,350. 1972 likely has the 2 piece rotor with pin type caliber. 1973 went to uni-cast. The absolute easiest way to tell whether ld or HD is to look at the lower control arm. If it has a large pocket for the coil, it is a hd. If the spring sits on top (like your current lower) it's a ld. Ld whether 100 or 200, uses the same ball joint. One of the biggest upgrades that you can make is finding a sway bar, especially if you can find one on a 300 or 350. I would stay away from jy coil springs. All the big parts stores can get you a new set at a reasonable price.