So my solution (which has worked so far) was to install a Scully Snorkel in place of my old fill gauge. It wasn't very expensive to buy, and it was easy to install. I capped the outlet at the bottom of the tank (didn't trust the 60 year old valve not to leak), and moved the PurePro filter to the top of the tank. I also added a Gar-ber screw on, oil filter style filter right before the burner. Replaced the old filter with a new element, replaced the pump screen, replaced the nozzle, and flushed out all of the lines. Once I fixed a minor adjustment issue with the Suntec pump (it would prime but not pass oil through the pump), we were good to go. So far, the burner is still working 24 hours later (whereas the last filter change plugged in 12).