.045 if you upgrade the HEI module to a higher power one you can increase the gap upto .060.
The Spark Plug gap is .045
Per Champion spark plug applications chart, the gap for 1989 Chevy 305 (5.0L) is .035.
0.045
.045
It is important to gap the spark plugs at the right size. The spark plug gap for a 1981 305 Monte Carlo is .045 inches.
Spark plug gap is where spark plug spark discharge is designed to take place. On a conventional spark plug, it is the area between the center and the ground electrode.
.045
.045
.45
.035
.045"
.035