well the only gilmer belts i have seen for your desired application are 1" wide, and designed for dry sump oilpumps. cog belt drives are not as neat as you might think. the belts have a nasty tendency to shed teeth as they age, and when that happens all your accessories work either intermitantly, or not at all.
oh and they dont last nearly as long as regular V-belts or serpentine belts do, as they were designed for race applications where they are being replaced on a regular basis.