If it is the stock engine, when you buy the plugs, the parts person can give you the gap. Many of the newer type spark plugs are pre gapped so you dont have to do anything to them. Hope this helps.
100.5 mm
0.060 inch
BAD coil, Plug wire or spark plug. Check these things and replace as needed.
0.060 Plug gap.
.060
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0.035
.40 gap
The 1998 Chevrolet Silverado V-8 engine spark plug gap is .031. Most spark plugs come pre-gapped from the spark plug manufacturer.
.035
,030"
0.060