Get some ARP studs in there and pull her flat!
![Smile :) :)](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
Besides, what's it gonna look like after you've dumped the skinny pedal on it 1/2 dozen times? There is a reason the Right Stuff comes in a tube!
Not nearly the same investment, but I've got a DIY4X4 fab'd D60 diff cover more warped than that. So far it's taken one trip to the machine shop to try getting it flat on their exhaust manifold surfacer (ginormous belt sander) and then putting it in the press to try to bend a low edge high. And now to surface it again, only that shop isn't accessible to me any more.
So, I agree with the statement made above, surface it
after cutting & welding.