Does anyone know a good online car stereo site with custom mounting designs?

From the looks of your photo, there should be plenty of pre-made mounting adapter kits for that dash, available from dozens of car stereo suppliers, both local and online. You mean that the oval spot for the factory tape player is where your empeg is right now, right?

I'll bet you could go to www.crutchfield.com , or www.tune-town.com , or to a local car stereo installation shop, and they should be able to get you the exact part you need.