After digging through a few threads on the matter, I'm still somewhat confused as to the differences between early and late front suspension. I'm getting that the spindles are different and, as a result, I'm guessing that the brakes are and the tie rod ends might be. What other differences are there?
Next question...which the first question might just answer: Is there a difference in the subframes where the control arms mount? If one were to swap everything outboard of the subframe with, say tubular a arms and other aftermarket hot rod/Pinto/Mustang II/streetrod parts, would that be a bolt in replacement which then opens you up to many more front end possibilities?
Entropy,
Brian walsh posed the same question in a thread titled "71 front suspension" on the 14th page of General help. It's never been established that the subframe pickup points are geometrically identical between a 71-72 and a 74 and later. There was some indication by Pintony that the Track of the front end would be wider if the later arms were used on the early chassis.
I would like to do the same for my 72, so I would like a clear decision or complete parts interchange.
Pintosopher
i take it that the later model arms/replacements are generally easier to get?
the track change really shouldn't be that big a problem. I know it is money but why couldn't you just change the offset on the wheels to get it back to where you want it to be?
do the aftermarket arms accept ALL year steering knuckles/spindles?
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"
Suspension components are no problem at all to get for a 74-80 pinto or 74-78 MII. However when checking them out, I could not find lower ball joints at all for the early suspension. The rest of the parts I could find but they weren't even in the O'reillys warehouse here in Springfield MO. They all had to be ordered from somewhere else. Now with all this said, I don't have any early model pintos, I was just looking this stuff up for another member. I wouldn't buy an early pinto myself because of this. I don't imagine it will be too long before you cant get any of the suspension parts for them. :(