I looked in some old city directories: 1931 - No BUSSELL in Modesto, Turlock, or Turlock Rural routes. 1935 - same as 1931 1941 - J Henry Bussell living at 640 Kerr Avenue, Modesto. No Clarence in any of the categories above. 1946 - No Bussells in any of the three listings. 1948 - Clarence and Ruth living on Rural Rt. 2, box 369. 1950 - Clarence and Ruth living at 342 Stanislaus, Turlock.
The directories are usually a year or so behind reality. It takes a while to gather the data, and they put the upcoming year on them, the way magazines date themselves in the future so they don't look outdated on the news stand. I'd bet the 1945 date for the move from Corona was accurate, or at least more accurate than the 1930 one.
Clarence didn't advertise in the "Veterinarian" section in any of the years he was in the residential listings.