(I just posted this over in sci.engr.lighting.)
To get the amount of light you'll need from standard incandescent is
going to take a lot of power and many many bulbs that will need
changing often. C7 lamps would be my last choice! I'd rather put a
transformer in the cove.
My recommendation is a little on the pricey side: Dimmable
The best dimming ballasts (IMHO) are Lutron HiLume and can be ordered
as part of any kind of fixture you might want. There are also a good
number of fixtures built to mount inside your cove. They have just
right reflectors and will minimise the shadows between lamps.
For example: http://www.lamlighting.com/pdf/cove_pdf/HPD%20Brochure.pdf
Especially with a less than white ceiling, you need some serious
lighting power. (Yes, they come in 3' lengths.) Knowing how much
is a detailed process, getting some skilled help is highly
Richard Reid, LC