why you are suggesting using a 74LS07 instead of the simpler option of a voltage divider?
Voltage dividers can often slow down the rise time of the edge given the capacitance of the input. On the Ada wave shield their version 1 had voltage dividers but they changed to level translators for version 2 because of the trouble the users were getting with dividers. With a buffer ( which I already had so that was a plus factor for that part ) the falling edge could be very fast and the rising edge controllable by the size of the pull up resistor.
I used this arrangement on my SpoonDuino, worked first time. 