Chris,
Distributor cap: The horizontal variety is original but rare. Both work fine.
Engine mounts: The "packet" seems to be assembled correctly. The coil spring preloads the leaf springs together with the fibre material which acts as vibration damper. The weld marks are from the cup-like washer which was welded to the part 31-5364 and where the lower rubber block sits. There is no need that the washer is welded on, as the long 10 mm bolt is holding all together. The drawing in the hand book is not very good and is missing the top rubber block.
On my picture 4948a the washer 31-5361 is not the correct one, it should be cup-like. The mounting arm locks different to mine, are they "after-market"? The original ones are forged steel.
For replacement of the rubber blocks, look for industrial shock mounts of 40 mm diameter and about 40 mm length or more. Cut off the metal parts and drill a hole of 10-11 mm lengthwise for the long bolt. You might need to carve off some rubber at one end, as it should fit into the cup-like washer. Looks a bit crude but works well.
I hope that helps.
Karl