Either Motor Warehouse in Sacramento, they usually just deal wholesale and not to the general public though.
Or my favorite is Bailey Bros. In American Canyon. They can really turn a crank. Not
The cheapest but very good and understand the ins and outs of older crankshafts.
I have them grind and straighten all the Model A and B cranks that I weld counter weights
onto.
They have also done a lot of work for Stan Vermeil over the years.