Heres the stock firewall. Were running a Hilborn Injected Nailhead with a Joe Hunt Magneto which will need a little clearance.  Were going to leave the Xs, just shortened up a bit.

At this point weve cut out the section that needs to be relieved and shortened up the Xs, now just need to make a nice curved piece in its place. The object is to keep it looking as original as possible .
Heres what we came up with. Hopefully it looks like it could have came from the factory this way.
The top area is curved also.  Little more work, but looks a lot better
. Now we have a little extra room.