The LG4 is the carbureted 305 V8 — same Gen-1 small-block architecture as the 350 L98 but with smaller displacement and Quadrajet four-barrel carburetion instead of port fuel injection. It sat between the L69 high-output 305 and the LB9 TPI 305 as the price-of-entry V8 in the third-gen lineup. 1982 rated 150 hp net; later builds climbed to 170 hp net.
Plenum decodes the LG4 from the SPID engine line and cross-references against VIN 8th char H. By 1988 the 305 TBI L03 had largely replaced the LG4 in regular production.