It just depends on how much current the receiver is running to the headphone port, as you said it should be fine but vintage receivers are are not consistent from one model to another in that respect. The LCD-2 stock cable is 1/4" but they have a 4-pin option or you could go aftermarket if you want, there are also straight speaker pin adapter cables available (the typical example is the K1000 stock 4-pin cable and speaker pin adapter cable) but with the LCD-2 you would definitely want the resistor.
Sorry I went off track with the HE-6, that is the one that most requires speaker taps in general and I went on a tangent. The LCD-2 is more efficient than either HiFiMAN but does like some current. In general most vintage units will be adequate, especially compared to more modern units out of the headphone jack so I think you're on the right track.
Very true, even all the 1250's aren't all the same. Any idea where i can get a resistor?