With no overboard discharge, you will not need a vented loop in the waste line. Capttb''s response is right, except I agree with alanporter that you won''t need to locate the tank inlet below the toilet outlet (virtually impossible on most sailboats that I know).
If you are using lake water to flush (i.e., a thruhull), you still would be prudent to include a vented loop in the intake line. There are a lot of boats that fail to do this, but if the pump seals were to fail, you could siphon the lake into your boat. WHOOSH is right about the placement of the antisiphon vented loop, but that is frequently tricky with a head like the W-C you have. The toilet will still work with the vented loop between the thruhull and the toilet pump, but you will have to give it quite a few pumps to establish a prime and you''ll hear a nice squeal as the air escapes from the duckbill flap in the vented loop.