Engine Mounts, sold each
DOSAAF mechanics in the field would often not change the two rubber engine mounts near 2 and 10 o'clock because the proximity of the Magnetos made them hard to get at. This can be seen as almost justified, in the light of gravity taking the greatest toll on those engine mounts closer to 12 and 6 o'clock.
And so it was that distributing sets of 14 engine mounts to Aero Clubs became commonplace, (whereas a full set would be 18 pieces).
You, on the other hand, can buy as many or as few as you wish.
One clear indicator of engine sagging is evidence of fretting where the engine baffles' insulation meet the inside of the cowling sheet metal. As stated elsewhere, there are no winners with engine vibration, and these rubbers are not hard to replace. At the very worst a cherry picker might be enlisted to take the load while those mounts close to 12 and 6 o'clock are replaced.