Thanks to the street rodders love of the Mustang II (late Pinto) front suspension, there are all sorts of goodies made for it, i.e. tubular arms, different length arms, new spindle forgings, 2" drop spindles, coil over conversions, several brake combos. The early and late models suspensions are of the same basic design but the later is a little beefier with slightly different dimensions so not much will interchange. I took some rough measurements with a ruler to compare 71-72 and 79 components, see below. The measurements preceded with a ~ were eyeballed and could be off by over an 1/8". The nut sizes followed by a ? seemed to be between normal sizes.
upper A-arm
length from inner shaft centerline to center of ball joint pivot: 71-72 = ~7-7/8", 79 = ~7-3/4"
width of inner pivot shaft frame mounting holes, center to center: 71-72 = 4-1/2", 79 = 5"
inner pivot shaft to frame bolt size: 71-72 = 1/2" w/ round shank, 79 = 1/2" w/ diamond shank
ball joint nut size: 71-72 = 9/16"?, 79 = 9/16"?
lower A-arm
length from inner pivot to center of ball joint pivot: 71-72 = ~12-1/8", 79 = ~12-3/8"
width of inner bushing: 71-72 = 3", 79 = 3-3/8"
inner pivot bolt size: 71-72 = 1/2", 79 = 1/2"
ball joint nut size: 71-72 = 9/16"?, 79 = 9/16"?
strut rod
length: 71-72 is about a 1/4" shorter than the 79
rod diameter: 71-72 = 0.68", 79 = 0.80"
frame end nut size: 71-72 = 9/16"? coarse, 79 = 9/16"? fine
A-arm end nut sizes: 71-72 = 3/8", 79 = 7/16"?
A-arm end bolt spacing: 71-72 = 2-1/8", 79 = 2-5/16"
spindle
distance from top of upper ball joint hole to bottom of lower ball joint hole (not vertical): 71-72 = 6-7/8", 79 = 7-11/16"
vertical distance from bottom of lower ball joint hole to spindle shaft center with spindle horizontal: 71-72 = ~2-1/2", 79 = ~1-3/8"
steering arm ball joint nut size: 71-72 = 3/8", 79 = 1/2"