What locking cap does everyone use? I recently ended up with a tank full of watery gas after leaving my '67 out in the driveway over night. I bought a typical locking cap from the parts store (the push in style which I know is correct for the neck) but it's too big around to fit inside the filler neck "shroud". Does anyone make 1 that fits or do I need to "modificate" this one? Any help or advice would be most appreciated...other than telling me it's time to move to a new neighborhood.