An OS 140 RX doesn't need anything special. Just run a fuel line straight from the clunk with one filter.....tee it and install a dot for fueling or run it outside and make a break point for same....and just run the vent line straight out the bottom of the plane. Nothing fancy is needed.

Some put a loop in the vent line, some use a check valve, etc. To me this is dead weight and unneccessary in my experience, but if it makes you feel better do it

-Mike