Im currently finishing the resotration process of my volvo 1800s and i have a doubt.

THe car came with the servo 670921

THe thing is that i cant find new servo like 670921 for my car, because everything takes me to the servo 686544.

Do you know if there's a difference between them?

Can i buy the servo 686544?

Kind regards

PS: My car has dual circuit brake system