Chiphead,
From my research yesterday, the thrust washer appears to have been used on 216's and 235's from 1937 thru mid-1955. It doesn't appear to have been used after that. It looks like it sets on the top of the oil pump drive housing.
Since the distributor drive gear runs directly on the end of the oil pump drive housing, I'd be checking how they fit together. The oil pump appears to have a recess machined into it to hold the thrust washer in the picture. Does your pump have the recess and does the gear fit down into it? The late '55 thru '62 pumps (that didn't use the thrust washer) may not have had the recess.
I assume that GM doesn't redo cutaway drawings unless that have to so the picture is probably of an earlier 235 even though it's in the '61 manual.
