I will also recommend a three line setup. I don't know anyone who uses a two line on gas engines. The line stays primed if you have a dedicated feed line, and I also feel more comfortable keeping the pump diaphragm wet. Also when using a two line setup with a tee, filling between the felt clunk and the carb is a certain way to let contamination in. If you are careful you may avoid it but with a three line setup the chance is eliminated along with possible air leaks. Who wants to do a carb rebuild just because they pushed a bit of crap in when they were refuelling, it is a much more involved job than on a glow engine.
good luck
Paul