Question about Climate Control Units...

I have an 86 Cutlass Ciera, is the climate control unit from an 85 or 87 compatible with an 86? They look exactly the same, but I'd like to make sure.

I need to buy one, I STILL have the damn hissing sound coming out of mine, nobody seems to know how to fix it... so I'll just get a new unit for around $40 and have it switched out.

Thank you!