[Mondial]

Yes that should get you close enough to see if the circuits are at least working. The only problem with connecting the scope to the cap of the 6K7G mag tuning amp is the capacitance of the scope probe will detune the 77A tuned circuit a bit. 

If you can see IF signal at the 6H6 plate pin with the scope, then you can tune 77a without loading the 6K7 grid with the probe. Also the same 77A tuned circuit provides IF signal to the AVC rectifier, so you can also tune 77A for max AVC voltage from the 6J5G AVC rectifier. From the top of the chassis you could probably see the AVC voltage at the grid cap of the first or second IF amp 6K7G if you use a 1 meg resistor in series with the voltmeter to prevent loading the tuned circuit.