same as 84 c-10. The computer is Located behind the glove box mounted under dash in that area(metal box with wires going into the engine bay). Look up ESC computer. It controls spark through your distributor and when it goes out it gives all kinds of false symptoms from bad timing to fouled plugs. There are a few write ups on how to disable it on this forum and the link below.
http://www.73-87.com/7387garage/drivetrain/escrepl.htm
I ditched mine and ran a HEI distributor and I also helped a buddy run his stock distributor by following the directions given in the how to write up.