a904 and carb help!

oh wait
If the governor flyweight has separated, it will never command a shift.
Additionally,
If the KD lever at the trans is fixed in the rearmost position, then the trans will want to stay in low gear to a really high rpm. Depending on the governor, it could be 5000rpm or more.
This is often done if the KD mech cannot be made to work. The usual obvious symptom of this is that the trans shifts very harshly from N/P into First.
In a Mopar trans, the Primary function of that KD mechanism is to control the Throttle-Pressure, and the KD feature is actually a secondary function. Therefore, if the lever is Not working by the throttle linkage, then it must be tied back to some degree, so that the trans will not fail if the engine is given too much throttle. But you can drive it "normally" for thousands of miles, by just staying on the bottom 50/60 percent of the primaries, with the secondaries defeated.