I fitted a 100R resistor in LK4 ('I' input)
and 100R resistor in LK 2 ('Q' input)
That is exactly the same as a Model 'B'
The 'Q' signal on a Rpi 2 is available on pin 35 of the header, so the only 'Mod' needed was to connect pin 23 and pin 35 together on the Pi itself.
If you plan to use the pi for other uses, look at Dave's posts above.