[HoodStrype]

The 86 is a two piece dash... but still a beyatch. I had an 86 & paid $400 to get someone else to do it for me. You can usually tell if it is the heater core if a "mist" (antifreeze) is coming through the vents. Also, check the two hoses that go into your passenger side firewall... they should be hot. If they are not, you either have an "air burp" in the line or you need a new thermostat if nothing is coming through there... Good Luck!

PS- My 89 has a busted heater core so I feel your pain!