I am working with 40 year old plans that call out AN365-6 Nuts.
Since they are used in conjunction with AN6 Bolts (24 of them) to
attach the main spars together, I am assuming they are locknuts.
Is the AN363-624 Metal Lock Nut a good match or good substitution?

Gotta have something to hold 49 feet of wings together.
Prue Super
Circa 1963 Standard Class Sailplane.
15 meter all metal 35:1 L/D

Clark