You're right. There is no such part as 3492 or 3493. 3492 should be renamed 3490, 3493 should be renamed 3489.
Complete assembly is 75172, and it seems that spring (our part 519) is 70181, the same as in the 4518 forklift arm assembly.
Complete assembly is 75172, and it seems that spring (our part 519) is 70181, the same as in the 4518 forklift arm assembly.