GM Computer interchangability

[Chief]

I wanted to borrow my friends Hypertech chip and thermostat to put in my 84
MCSS 305 HO.  He has and 85 MCSS 305 HO.
I tried the chip and thermostat.  Gives a code saying incorrect prom.

Checked with Hypertech, and the 84 uses a different chip than the 85.  So
then I call the local Chevy dealer.  He says that the 84, 85 and 86
computers all have a different part #.

Did Chevy change these computers from year to year just to screw with things?

Does anyone know the difference between 84, 85 and 86 5.0L HO computers and
can I just switch in an 85 computer to make things work ok?  I assume all
the sensors are the same from year to year.

Any help would be much appreciated.

Thanks.


Ed Hilker aka "Chief"
84MCSS 700R4
Gainesville, FL