Need to know what year.
.017, or, a matchbook cover, works great.
depends on the ignition system you're using. Hei
small block Chevrolet with HEI ignition is 45
The gap is usually about .016", but it should be set at 30 degrees with a dwell meter for optimum accuracy.
0.019 point gap
If it has points then it is .019, You must be working on something old.
.017.
Chevrolet covers all V8 sizes with a gap of 0.035 with plugs (Optional) R44T..Ralph Maldonado
.035 or you can go .045 depends on the engine setup but .045 is a safe gap.
set the point gap to achieve 30 degrees dwell.
that should have the HEI distributor so the plugs should be set at .045