Joe et al,
Thanks that is what I was after, especially about the 396.
Turns out I didn't leave the lever unhooked, I just set it up so it didn't quite kick down all the way.
That shifted about 4200rpm with the 250-4v.
When I made sure it would kick all the way down to the stop, it would shift at 4600rpm.
As noted, the part-throttle behavior is very sensitive to where the lever is set, and how much travel it is given. The Ford c4 and c6 kickdowns don't affect part-throttle behavior but the powerglide sure does. So, now I know.
