Under the hood you will find a placard with the Spark Plug Gap listed.
If your're using ACDelco Platinum Spark Plugs the gap is .040".
The instructions on how to install spark plugs from ACDelco can be found on the website of the company. Precise information and instructions can be sought under the section spark plugs of the website.
Spark Plug (ACDelco R45TS) [Gap @ .035” for points distributor, .045” for HEI distributor]
gap is 0.60,
( .054 inch ) for the 4.0 liter OHV , 4.0 liter SOHC , and the 5.0 liter V8 engine
ACDelco #41-601 conventional spark plug gap .060"
Spark plug gap for a 1977 Corvette using ACDelco R45TS is .035
ACDelco 41-103 Iridium
ACDelco R45S conventional spark plugs for an original ignition system.
ACDelco 41-601
.044 inch
ACDelco conventional spark plug 41-601, .060