Out of curiosity did the 55.2 + short bed truck ever have side mounted tires? Or was this only for long beds pre 55.2?
First, the bed-side-mounted spare tire carrier was available on all sizes of trucks with beds in 1953 through 1955-1st. And, there was no such term as "long bed" for Advance-Design Chevrolet trucks.
Regarding 1955-2nd+ trucks, have you look at specifications manuals available at the GM Heritage Center? Those manuals show options available for all years and sizes of 1955-2nd+ trucks.
Yes, the bed-side-mounted spare tire carrier was available on all sizes of trucks with beds in 1955-2nd (my guess it was also available in later years, since the dimensions of the beds did not change for many years). I see a 3200 (long-bed 1/2 ton truck) listed for 1955-2nd but no spec-page for it. Other sizes of pickups show the side mounted carrier.