It's not a direct swap, but really isn't a hard one. The biggest problem is wiring the gauges & heater controls if keep the 86 harnesses. You will need to modify the mount points on the body at the top of the dash where it meet by the windshield. Have to bend a few tabs and trim one alittle and use a little longer screws.You will see what I mean when/if you do it. Also you will need to move the e-brake handle over and trim the hole where the cable goes through the trans tunnel for the center console to fit. Also have to add the back mounting bracket for the center console, the one the arm rest bolts to. No biggie there just find the right location and use some self tapping screws.
But back to the wiring, if you are using the 86 hanress you will need either to splice the 86 harness with plugs for a newer harness for the gauge cluster & heater controls. You can run aftermarket gauges, or swap the dash harness. When I did my 86 I re-wired the whole car with 89 harness(front to rear), mainly because my car's harness'es were in bad-bad shape when I got it, and plus I wanted mass air. There are probably some stuff I have forgot, it has been about 2 years since I did the swap.
The dash itself it easy to swap in, just the wiring can be troublesome.