I also needed a fill vent. I put a 3/4" vent hose on the tank for a reasonably fast fill and I needed to graft that to the filler pipe near the cap. There is another 5/16" vent in the tank with a roll over valve that is the running vent, the large vent isn't open unless the fill cap is open. I had to be able to fit the vent through the cap mounting hole in the body, so I had to make a very tight bend. I would up making a 90* tubing connection.

I started by swelling up a piece of 3/4" tubing to keep the hose on. I used a modified 5/8" bolt and the hydraulic press. Worked out fine.







Next I whittled a short section of 3/4" square tubing to take the round tube and welded the parts together.