Tim,
I just finished doing that on my -4. It seemed like a small job but turned into one big pita. I used a 90 degree fitting going into the back of the Vans gascolator. My output line from the aux pump comes from the left side of the cockpit inner tunnel and out the firewall in another 90 degree fitting. A short length of tubing about 6" long joins the two fittings. Between dodging the engine mount, the exhaust pipes and the throttle and mixture cables there just isn't much room. Plus there has to be room for the fitting on the back of the gascolator. I fabricated a mount that holds the gascolator slightly farther out from the firewall than in your installation. This mount attaches just inside of the right cockpit inner tunnel wall, about where you have yours. If I had it to do over I think I would have gone with a racing filter instead. Good luck!
Alan
RV-4 N7028K