I can't help with the rail beyond suggesting filing/hammering, etc.
But can I ask what you want to scope it with? I've found the one piece mounts to be perfect for 40mm.
I recently wanted to mount a 32mm and used these guys - they're MASSIVE for individual rings. and each one is held on by a pair of bolts.
Amazon.com : Hawke Match 1 Rings, Low, 3/8 to 11mm Dovetails : Sporting Optic Mounts : Sports & Outdoors