When replacing a section of boxed frame, is it necessary to brace the butt welds?

[cjsgarage]

Hey guys. I'm just wondering if any of you has some advice.

I'm having to cut a section of frame rail out of a 1957 Ford to change the front suspension. The frame is factory boxed, and has large pockets for the coil spring to sit in. I need to cut the swelled coil pockets out of the frame and put in regular 3x4 box. The 3x4 box will match the rest of the frame. But when I've installed C notches and other frame pieces (after having cut out a section) I've always braced the butt weld. But that's been on c channel frame rail which got boxed after the bracing was done.

Is it necessary to brace a box tubing frame rail? Would that be accomplished by sliding in flat pieces on the sides and drilling a hole from the out side to plug weld the brace?

Am I being too ambiguous?