When set properly, the gap would probably be about .018". The correct way to set the points would be to hook up a dwell meter and adjust the points for 30 degrees dwell.
0.019in
a 1973 Chevy truck has HEI Answer And if it does have points, say not the original engine, its .018-.019 will do.
i know on a 75 Chevy scottsdale with a 350 it is 35 thousandths
Use a dwell meter to set the gap at 30 degrees.
Use a dwell meter to adjust the points to 30 degrees dwell.
Spark Plug (ACDelco R45TS) [Gap @ .035” for points distributor, .045” for HEI distributor]
.045.
On my 1992 350 van it's .35 gap
.060 thoundson gap
.045 spark plug gap
points .035 HEI .45 Rick ASE L-1 Master TransMichigan.com
The 1989 Chevrolet 350 cubic inch engine spark plug gap is dependent upon the engine application. The most common spark plug gap for the Chevy 350 engine is .027.