0.035" is correct unless/until you start improving the ignition system (
HEI upgrade ). They probably are gapped at 0.035" out the box, but it's wise of you to check. A ramp-style gap gauge like that (or any other flat-style gauge) is almost worse than useless; to check spark plug gaps accurately requires a round-wire gap gauge like
this:
View attachment 1715146206
Dielectric grease ("tune-up grease", "silicone grease", "spark plug boot grease") is a good idea. Just a little dab'll do ya on the plug terminal and porcelain; it doesn't take much, so don't be a paste-waster. Rotate the plug wire boot a little as you install it to spread the grease around, but don't go crazy and twist off your plug wire ends.