I have a couple of FS2004 planes that work well in FSX except,for the gauges which are in a format no longer supported.Can I put FSX gauges in a FS 2004 plane? Easily? Thanks
Sure, I guess. I don't fly FSX, but you should be able to just open up the panel file and replace the offending gauge names with ones that work in FSX. Don't mess with the sizing or placement, and everything should work out alright.
Get a copy of FS Panel Studio available here http://www.fspanelstudio.com/  & changing gauges around is simple....I used CfgEdit with FS98 thru FS9 but FSX requires an upgrade.