The quality of the output from raw on D1 will exceed the requirements for resolution in magazines. However, if the stock photos are for some higher resolution need (large blow-up trade show pics, higher end books, etc.) the resolution would likely produce a picture that is not very sharp. But resolution and sharpness are not the same as pixel size. In PhotoShop you can blow up a D1 image to any "pixel" size you like. Film shot without a tripod may show some camera shake and not be sharp because of this reason. So film will not necessarily be "sharper" than digital. A slower speed 35mm color film shot on a tripod will tend to be as "sharp" as approximately a 20 MB digital image from a digital camera back. In order for film to be "sharper" you would have to move to medium format film.
The bottom line is you would likely have to send them a 50MB D1 image and ask them if the quality meets their needs. It is entirely possible that they will say yes.
To some extent, the only way you will know is to ask them.