Use a dwell meter to set the points at 30 degrees dwell.
The point gap should be set for 30 degrees dwell.
Per Champion spark plug applications chart, the gap for 1989 Chevy 305 (5.0L) is .035.
The Spark Plug gap is .045
.45
.035
.045"
.035
.045
The recommended spark plug gap on a 1996 Chevy C1500 with a V8-305 engine is .060"
.45
I have an 84 305 and everything says 45, and uses r45ts plugs
.035