Inconsistent shifting: any ideas?

When racing, I am experiencing shifts all over the map from 1-2. Sometimes they feel crisp/firm, other times, "stock," and sometimes very soft. Starting in Low, shifting to 2 at 5500 RPM, then to 3 at 5500 RPM.
1973 Plymouth Duster
Torqueflite 904 with TF-2 shift kit (installed by my trans guy)
Mopar factory high stall torque converter (so 2500 or so)
Lokar kick down
3.55 Suregrip rear end
Powered by Mopar Performance Magnum crate motor (380 hp 360).
Here are some videos where you can hear the shifts. Please excuse my bad racing skills - still learning but much more concerned about getting the car to perform consistently.
1) 1-2 firm, 2-3 firm

2) 1-2 medium, 2-3 firm

3) 1-2 soft, 2-3 firm

4) 1-2 soft, 2-3 firm


Anything I might be able to consider doing here to get all of my shifts firm? It always feels firm during normal street driving!