Generally
1955 before chassis number 75300 these have anti-roll bars, you can look on the registration certificate or on the license plate it says the chassis number.
1 pair of anti-roll bars complete with bolt, tube sleeve, bushings and washers for both sides. They sit at the far end of the anti-roll bar.
Noise in the front trailer? A common fault is precisely anti-roll bars bushings and rubber. (Sold in pairs)