It wasn't so much the car line, it was the cars. The 1100's from St Louis were by far the bouncy ones; they rode as if they had no shocks/dampers at all, and anything over 30-35, in the tunnel especially but also on the street, resulted in a really bouncy ride.

The older 1000s (originally double-ended but single end at the time I rode them) had a smooth ride but tended to yaw a bit. Perhaps wheels were worn out (in the 1960s) or a little out of gauge? They also clearly didn't have the power for real speed in the tunnel.

The newer 1000s (single-ended from the start) were by far the smoothest-riding and fastest.

Suspect it was the Clark trucks on the 1100s that made the difference. Plus, of course, they were already worn out when Muni got them.