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I seem to remember my 1D2 producing jpegs at 72dpi and Raw at 240? dpi
I believe my 5D2 does 240dpi for either jpeg or Raw
Check your 5DC out and see if it changes. If it does, I would suggest shooting Raw for the files you know you need to print larger.
Also look in your software i.e. photoshop because it may show very large pixels at 72dpi and when you change to 150, 200, or 300 dpi, the image will still show enough size for an 8x10 as an example.
Hope this makes sense for you.