Paul,
If I recall correctly, the 1958-59 Impalas could come with both the wide-ratio 3-speed (1st gear 2.94;1) or a close-ratio 3-speed (1st gear about 2.5:1) transmission as an option. I believe that all of the light trucks in 55-59 came with wide-ratio 3-speed. I don't believe that this should affect the interchangability of the tailshaft.
Hoyt
