I have the fender mount on my 69 fish and they work most of the time except for when they don't which is about 50% of the time. Through the years I've replaced the bulbs, sockets etc. and they work for a while then find some way to lose their ground or the bulbs get corroded or the wire falls off. About twice a year I pull em apart and give em a dose of WD-40 which seems to help. Another quick tip, I've had bad bulb contact in the past and I find if I put a bigger solder blob on the end of the bulb it'll make contact.
I didn't know about the fuel pacer option but it sounds like a bigger maintenance issue.