My references show the Wards Western Field as being the Savage 620A.
Given the SBP620A, I'd say this is right.
My very old copy of Gun Parts catalog shows the following on the Stevens/Savage Models 520 and 620, and the 520A and 620A:
"The 520A and 620A versions of these guns have shorter receiver and guard tangs and no tangs, respectively".
"Specify gauge and describe the parts when ordering".