Everything is different, nothing is interchangable.

The 86-89's use a Mcpherson strut front suspension and a solid axle rear. 90+ cars use wishbone type independant suspensions.

90+ aftermarket parts are common and mass-produced, making them cheap. 86-89 stuff isn't popular, production is low, and the price reflects that. Parts from a junkyard is usually cheaper for the 86-89 cars though.