With the carb at WOT with all barrels wide open, you have to adjust the TV to max pressure, by pulling the lever all the way to the rear,as BUD says.
If at part throttle, this now bang shifts too hard with that shift kit,or you don't like where the automatic upshifts are occuring, then you have to bring the carb pivot closer to the throttle shaft...... or reduce the line pressure. This will of course alter the automatic upshift speeds, so now you have to modify the governor pressure.
So yes you are quite correct, it can be tricky.
There is only one important adjustment; that the TV lever down at the trans, be all the way rearward at WOT. This is to maximize the holding pressure to the various clutches and servos inside. The more power you have, the more important this is.
In your combo, I wouldn't be afraid to experiment with the line-pressure. With a shift kit already in it, I think with your 300ish hp, you will have a bit of leeway.
You cannot adjust the line pressure without taking the pan off. To solve this, I drilled and tapped a small hole in the case,directly behind the adjustment screw,so I could insert an allen wrench there from the outside. This adjustment is very sensitive, so 1 turn is a lot. But during the initial set-up stage, 1 turn is about right. Install the access-plug-you won't be sorry.
For higher automatic upshift speeds than the TV will give you, you need to cut some weight out of the governor. This too is a sensitive thing, it's easy to get carried away by taking too much off, and then under part throttle, the auto upshift speeds can get to be too high.
To help your understanding;Here's the deal
The line pressure is the first go-to.It sets all the basic pressures for normal driving.
The TP (throttle-pressure,aka kickdown) increases the line pressure under full-power situations.and
The governor fights them both to cause as early an upshift as possible. It does this by varying the pressure in accordance with driveshaft rpm. The faster the d/s spins, the more pressure it allows thru and the earlier the shift command. It's flippin ingenious.
The TP is called the KD because it directly affects the upshift speed commanded by the governor, allowing you to vary the upshift-speeds with the foot-feeder. And yes, the kickdown speeds too,lol.
Now, go drop the pan, find the adjuster for line-pressure, and make the access port.GO! It'll be the best hour you ever spend on that trans.