The rear brakes will interchange but may actually be Girling vs. ATE or vice versa. The pads fit all models.
The body parts are not interchangeable except for doors. The front fenders take different turn signals and the hood has a different contour at the cowl- it could bolt together but wouldn't match up.
Struts should interchange, but look closely at the strut tubes on the 82, the early cars often rust out the seat for the spring with bad results. Suspension is essentially the same among all these cars.
Fuel injection's totally different. At best the 82 has the LH-Jet 1.0, and while it looks similar to the 86 setup, it shares no parts.
The interior is different but interchangeable. The seats bolt to each other's tracks but have for instance different non-interchangeable headrests.
The 82 is more likely to have good accessory instruments in it, ie tach, oil pressure, voltmeter gauges. Those are worth getting for the other cars.
--
Rob Bareiss, New London CT ::: '86 244DL- 215K, 87 244DL- 230K, 88 744GLE- 198K, 91 244 180K

Generally, there are a lot of mechanical parts that interchange. The body parts
are not usually interchangeable. Although the front fenders fit, and so would
the trunk. The motor and fuel injection are different enough that there are
only a few parts that interchange. The lighter bumpers of the newer car are
much lighter. The older car has a stronger motor. The earlier cars are usually
geared lower so the pickup will feel stronger. I like the older cars for the
cheaper parts. I think the older cars are nicer in some ways and the newer cars
are nicer in other aspects. For example the headlights. I like the older
headlights. (US look) On the newer cars I like the lighter bumpers and having
a rear fog light. Most all the interior is the same. Wish you well.

Dave 82 242ti