Vortec Inline Stand Alone Engine Harness - Lime-Swap Vortec Inline Stand Alone Engine Harness Available for all of the Atlas inline engines: 2800/2900, 3500/3700 and 4200. Send the engine harness out of your engine to be swapped, and we'll convert it for stand-alone use. Half payment is due prior to work start, half at completion. 1999 - 2003 VORTEC W/ 4L60E STANDALONE WIRING HARNESS Harness allows use of the factory Vortec intake manifold and multec injectors with flex-fuel injectors (EV6) optional. They are completely plug and play with four wire hookup (switched power, constant power and ground connections required).