O.d.
I've been driving a 1980 D100/150 that's had a somewhat built 69 440 transplanted in place of the factory slant 6 and bolted to the factory 833 O/D.
I've done plenty of "spirited" driving.
It's fine.
I personally would not power shift any transmission into overdrive.
When driving hard, I like to think of the shift pattern as a three speed with a better 1-2 throw.
Stay in 1:1 until you feel like relaxing, then shift to O/D and cruise.