we just did this. We went with the top-lever pump, not the through-bulkhead type. . We ended up with putting the pump inside the locker, screwed to the fwd wall of the cabinet next to the head.
We managed to get it so that the full throw of the pump handle just misses the sink pipe, but the door still closes.
Height-wise, we put it as low as we could on the wall section above the lip - it needs to be above the waterline.
This job took all day - we used white sanitation pipe for the 1st time and either it is a pain to work with, or i'm doing it wrong. Now we have it in it works very well - it was worth it. We have a 3 way valve to a holding tank as per the Lavac instructions. Just take your time and it'll go OK.