Here we haveThe Riley Four-Sixty Eight Service Parts List/Catalogue. Published by BMC AKD 954 (Binder Only). Vanden P Plas AKD 1416 4th Edition (inside folder). Make sure the part you are purchasing is the part you require, cross referencing is always.
The flat washers are the correct (table 3 heavy duty) type and of course bright zinc plated for long lasting protection. The spring washers are of the correct (rectangular section) type with the exception of the smallest (3/16) which are of the square section as was normal.