Howdy,
Any ideas how i could possibly fix the window sill here?

http://i1205.photobucket.com/albums/bb422/gumbi18/1957%20GMC%20half%20ton/002-1.jpg
http://i1205.photobucket.com/albums/bb422/gumbi18/1957%20GMC%20half%20ton/001.jpg

This is pretty much the only bad spot on the whole upper cowl panel so im not going to replace the whole panel, but I have no idea how to go about repairing this. My uncle mentioned using fiberglass over it all to build up the lip for the windshield and/or use bondo. I know most of yall are against using bondo for repairs but i think that this would be a challenge for even someone with years of experience, (something I dont have, first restoration for me). Im decent with doing metal work but I feel this is out of my scope to refab all this in metal.
Any ideas?