Cardon 77-5500 ECM.  We purchased this for our 86 El Camino with the EFI 4.3 V6 but never installed it.  It's is as-new, in the factory package.  Actual item shown. 

Please see photos for more details.

Make sure to check the shipping tab for more rates - Ebay doesn't always display the cheapest price first.

Thanks for looking!