Not sure about '70 E body 440's, but the ICCA 68-70 B Body Fastener Reference Manual shows a 5/16-18x0.88 SEMS Hex head bolt with a 0.75" non serrated loose washer.
A flat washer under a lockwasher defeats the whole purpose of a lock washer!!
Jim

Alternator bolt001.jpg
1970 Superbird 440-6bbl, auto
1969 Barracuda 340-4bbl, FB Formula S auto
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2022 Can Am Spyder RTL