Yep, that it the one I was referring-to, jorb
We have noted that "oddity" before, and wondered about the lifters.
The resto-pack also list the Powerglide as a truck transmission in 1960 (RPO 311 document page 5), as the 4-speed Powerglide.
In another location (document page 23) the Powerglide is listed as 2-speed.
