This system uses only two main components. A GM HEI 5 pin control module and a pressure switch. I have used this system on both of my custom turbocharged cars and it works well. A Bosch fuel injected 1980 Fiat 2000 Spider and a Weber carburated 1987 Yugo 1500 cc.
GM HEI 5 pin control module (e.g. 1980 Oldsmobile Toronado V8)
#15 Pressure switch with at least a closed and normally open contacts (e.g. Honeywell)
Piece of aluminum block for control module (Lowe's Hardware metal stock section)
Heat sink grease (Radio Shack)
Other items: vacuum hose, nipple, tee, metal bracket, brass tee, etc. if bracket is desired.