Wiring the engine is especially easy using a carb and GM’s factory coil harness, mated to MSD’s 6LS timing controller. The 6LS is a very versatile ignition controller in that it can be attached to the factory sensors and used with a carburetor (like we’ll be doing) or can be utilized to work in conjunction with a stock EFI application using an accessory harness from MSD (part number 88862). In both applications, the controller offers several programmable features that allow for RPM and timing adjustments via their supplied ProData+ software and a PC or with an optional hand-held programmer (part number 7550). Timing adjustments and selections can also be made with plug-in modules. Here, the main harness is attached to the controller (right), leaving a few wires disconnected. At the bottom of the photo, the black/gray wire should be run to a good engine ground source, while the pink wire is a switched 12V+ and the yellow wire is the tach signal. The connector at the upper right (pink and blue wires) is for a step retard for nitrous oxide applications and a two step signal to control two rev limits respectively.