U – 272 2BC (2 barrel carb), M would have been 272 182HP with four barrel carb
5 - 1955
R – San Jose, CA
G – tudor, fordor, Mainline, Customline - typo? C – Convertible, Sunliner
134309 – 34,309th in the production
76B – Fairlane Sunliner convertible
DX – D is Waterfall Blue but the X isn’t listed in my manual.
AY – Medium Blue and Light Blue Vinyl trim (interior)
05D5 – April 5 production, 5th car produced.
I believe the G is a typo. Should be a C. The second color for the two tone paint is not listed in my particular catalogue. The San Jose plant is noted for quite a few deviations from normal so the X doesn’t surprise me. Maybe someone else has the color code for X?

Lorena, Texas (South of Waco)