I belive its .35 to make sure go to a library and look it up in a chilton's manual or call your local Chevrolet dealers service department. They should know the answer for sure.
The Spark Plug gap is .045
Per Champion spark plug applications chart, the gap for 1989 Chevy 305 (5.0L) is .035.
.045"
.035
.035
.45
.045
The recommended spark plug gap on a 1996 Chevy C1500 with a V8-305 engine is .060"
.035
0.035
.045 inch , according to my Chilton book
0.035" ("35 mils") 0.889 mm