Strange, I added a/c on my '87 and used the same heater core.

 

I had them order the high output core to see it that will work. From the pictures it looks like the tubes are not in the right place so we will see. They may just use a stock picture for several cores.

 

Yup. Stopped to look at the high output core and it's tubes come out at a different angle and location. Not a chance it will work.

Sean- did you take all the AC stuff off another '87 to put on yours or just somehow convert what you had?

 

I took the a/c stuff off several trucks of various years.