If you still have the lever arm dampers at the rear you could try a heavier weight oil. Cheaper than changing to telescopic shocks.
Need to try this with my '76 car, particularly when loaded with Madame and a large'ish suitcase. grin2

Cheers,

Graham (G4FUJ)

Sold L44FOR 4/4 Giallo Fly
'11 MINI Countryman Cooper D All4
'90 LR 90 SW