What vintage are the levers Barry? The original ones had the back plate (with or without cable stop depending on age), the lever, the 'slotted' black steel washer, the bevelled chrome 'compression washer' and the fixing screw with the wire loop. Well, that's what I've got on mine anyway!
Later ones had a had a deeper 'well' in the lever to take a bevelled nylon 'compression washer' and an outer washer and the screw.
You can't mix levers between the two. I know. I've tried!