Some earlier 1949 designs were part bearing and part bushing. The pumps from 1937 through 1948 were all one bushing but some of the later reproductions have a double row bearing/shaft assembly. The seals may be a bit different on those due to the way the impeller is designed. This link from Carpenter's has an exploded view of the late type pumps for early V8s.
https://www.dennis-carpenter.com/tru...SABEgL1F_D_BwE
Those BB 458 kits are for the 8BA family of engines with the exception of the 1949 Mercury pumps.