EHT, I didn't have a factory stock for my 181, but a Choate folder made sometime before 1980 (not sure what the original owner did with the factory stock but wish he had included it in the sale). It was a great fit, but I wanted to go back to its original configuration. Closest I could get was a current factory wood stock. I did feel the need to shim with credit cards.
My 583 fit into it (the Choate folder) just fine. If nothing else, it was a tighter fit. I never felt the need to shim but in the end, I preferred the 583's factory synthetic stock (lighter, shorter LOP), to include credit-card shimming it.