There were no major frame rail changes, but a tower spacing change in 1979. The XD had a 1.5" wider, 61.5" track by virtue of tower widening and some new components.However, lots still interchages. The updated track rods got controlled wheel recession bushes, upgraded tie rods and bump stops, but the pitman arm and steering gear was all XA. There was a deformable front cross member, and an integrated firewall brace which makes the XD and XE's one of the harshest of Fords in the ride department.
The frame rails were the same as the XA to XC, the brake discs on an XD six swap over with an XC V8. The increase in track was all done by minor respacing the spring towers out in the producton line. This was ineffort to reduce turning circle, with large notches in the frame to clear the wheels. Didn't help much! Power steered XD to XG Falcon wagons had 13.2 meter wall to wall turning circles just like the XC.
There was a huge geometry improvement in the 1976 XC with the special upper control arms. It wasThe upper control arms were unchanged for the next 20 years and are interchangable with the XD/XE/XF/XG.
From my measurements, I don't think there was any change in frame rail centre spacings with the XA. Everything was shifted out by increaig the scrub radius and stub axles. Brake disc/drums there sat further out and contol arm offset was more. The rear axle was widened, but the leafs stayed in the same place. Front and rear track increased to 60 ", about what it was on the 1970 Torino, the cars being closely related. (Although the XA was the first Aussie styled design, by a Aussie Rosi, it was very much a Torino offshoot with, the Yanks pushing the Aussies to use the Torino platform) Steering box was different to the XR to XY, upper contol arms changed.
The XA was 1.5" up on track. The XR to XY was about 58.5".
The XW or XY got the big changes in a stronger upright to cope with the Kelsey Hayes ventilated disc brakes. It was basically the big block Fairlane spec.
