I believe there were different size balancers used depending on the application. The main thing to be concerned with is the balance of the engine & the timing mark locations. A 350 is an internally balanced engine. You need to be sure to use a balancer for an internally or neutral balance rotating assembly. The 400 SBC was an externally balanced engine. The balancer is different for these engines. You also need to make sure the timing mark is compatible with the timing tab you are using.
I hope that this helps. I am sure there is more detailed information available on this subject.