A 4/4 of your era has front springs that are insufficient for the job in hand. Many have upgraded to heavier duty springs to good effect. The factory shock absorbers are not great either.
I have upgraded our 2014 4/4 to adjustable AVOs and it made a big difference but did not prevent the bottoming out. When the King Pins are changed, I will be having heavier duty front springs fitted.
Tim Ayres will be able to advise on all counts.