Sight Fuel gauge

I am looking for 337 where someone converted a PA-18 or PA-22 from electric fuel gauge to Sight gauge. I am rebuilding a Colt and want to mod for site gauge. Is it a common practice to convert the newer PA-18's in this manner?

Thanks
Jim Miller (Tennessee)

I've got the go ahead from the FAA to do it on two Clippers. Haven't got that far yet, still working on fuselage sheetmetal.