Originally Posted by RealWing
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

Been in machine repair for 45 years and have always used flat washers with lock washers. The flat washer gives something for the lock washer to bite into. Just my 2 cents.