Hot Rods C notch steel size ?

I'm planning to c notch a '34 frame 2 " to allow more travel for an 8" Ford differential. Any recommendations on what size round steel pipe to buy? minimum thickness/maximum thickness, or?

 

3/16" wall tubing for a simple c-notch, many use 3/16" plate and make a "sweeping" C.

 

I'd go minimum 3/16" and fish plate the frame for additional strength. If frame is boxed I'd cut a length wise relief on top and bottom and slide in a section of flat plate that has been trimmed to a size smaller than profile of the frame and weld it in top and bottom as well the 'C' notch or sweeping notch as DDDenny stated for added strength. If not boxed, the plate could be inserted like step boxing and welded in before boxing. You could always fish plate the frame as an alternative for added strength. I'm just to our rules and engineering requirements down here.

 

This.

 

This is what I call a sweeping C notch, fellow HAMB members' 36 roadster.

 

Someone here posted this link about C notches......
http://67-72chevytrucks.com/vboard/showthread.php?t=457037