I spent some time researching the proper hardware for the clutch/pedal assy and shifter assy and didn’t find a few wave washers sold by parts houses. I also didn’t have much luck searching the ford part # in google, so maybe if someone searches the number in the future, this can help.
Ford part # 356573-S wave washer - AMK .39 ID x .75 OD (part # B-11591). Two used on lower clutch rod attachment to Z bar in '67 390 car. Also used on 4 speed shifter rods (351467-S), 6 here required IIRC. The ones here are closer to original size than the ones offered by NPD
Ford part # 353574-S wave washer - AMK .64 ID x 1.0 OD (part # 11323). Used on brake pedal mount to pedal support. This one is strange because the diagram seems to show the washer sandwiched between the bushing (2471) and the pedal shaft. The .64 ID is too small to fit over the bushing, so I mounted it outside the bushing against the pedal support. I figure keeping the bushings in place on the pedal shaft is beneficial?
Diagram from WCCC
1967 - 1968 Clutch Linkage and Equalizer Parts at West Coast Classic Cougar :: The Definitive 1967 - 1973 Mercury Cougar Parts Source (cougarpartscatalog.com)
4 Speed shifter box wave washer
Ford part # 379575-S. I found a similar one at willie washer (part # 1.687-1.000-.020X2-3)
Previous thread here
68 J Code 4-speed shift linkage part - Cougar Community / Classic Cougar Maintenance Restoration and Repair - Classic Cougar Community Forum
Hope this helps someone in the future
Sean