Early A-body Headers

I know they are not the best flowing header out there. The Doug's and TTI's flow much better and cost more. These are to be better than stock manifolds, no more, no less...except cost!
I've spent the last six months restoring perfectly the whole power train in my '65 GT. The last huge score was finding seperately an actual correct 8-3/4 rear with the 10" drums and located a perfect suregrip. I went high and low to find original power steering and the correct front rotor system that then of course caused me to go up to the 14" wheels with the small bolt pattern. I have been fighting my Mopar cronies tooth and nail to spend stupid to build it up to be as close to original as possible. I am finally breaking down to admit that I've got to modify for dual exhaust. This business of cutting away the piece of structure on the right side of the unibody to accommodate the right pipe and then rewelding a structural piece around it gives me the willies. Everybody says it's no big deal I just don't know who I would find or find pictures or plans on how to do it the smartest way. Most importantly, I probably would go up a size on the dia. of the piping but does this make any sense if I stick with the original cast exhaust manifolds?