I don't think I've ever seen one. They did have some valve covers with raised necks on them, but they were "permanently" attached, meaning they didn't easily come off.
But maybe someone else knows of an extension, perhaps from the aftermarket?
You might look at an E-series, they had a long filler that extended to the front for easy access. It may require an E-series left valve cover. The 460s had a short (2-3") extension in 1986, maybe other years in the pickups, one end went in the valve cover and the cap went on the top.
"Getting old is inevitable, growing up is optional"
Darth Vader 1986 F350 460 converted to MAF/SEFI, E4OD 12X3 1/2 rear brakes, traction loc 3:55 gear, 160 amp 3G alternator
Wife's 2011 Flex Limited
Daily Driver 2009 Flex Limited with factory tow package
Project car 1986 Chrysler LeBaron convertible 2.2L Turbo II, modified A413