403: a couple of queries
 

Looking under the rear mudguards I've noticed four rectangular tabs about 1" by 1/2" around the inside edge. What are they for?

The rubber seals on the wiper stalks are shot. Are they the type that press into the scuttle or should they sit on top of the body?

There is an alloy inner wing riveted or screwed to the steel inner wheel arch inboard of the rear wheels and on its outer edged secured in place by the tabs you describe.
The rubber seals for the wiper spindles need to sit round the shaft and through the body, they are available on eBay and possibly also from BCL, I never checked buying samples from eBay till I found ones that fit.
To ease installation it helps to slacken off the mounts to the wiper rack wheel boxes.
Geoff.

Thank you Geoff. You made one slight mistake:
There should be an alloy...!

I have ordered a pair of Standard 8 seals of E-bay and will see how they fit.