Assuming that the PAL video and NTSC video have the same number of frames (i.e. it's only the framerates that are different), then you can work out the adjustment from the fps: 23.976* for NTSC, 25 for PAL.
The PAL audio needs to be slowed down to 95.904% of the original speed (i.e. 4.096%).
After conversion, the total running time should be longer by a factor of 1.0427.
* Actual value used on NTSC DVD = 24000/1001