I wouldn't call them headers, but I made a set of tubular log-style exhaust manifolds for my BB early A-body not long ago. Here are some lessons I learned that I'll apply to when I build a set of proper long tubes for the stroked big block.
Some people only weld the outside of where the tube enters the flange. For me, welding both sides is the way to go and makes the joint way stronger and less prone to cracking.
Go into it knowing it's going to take time, so you're not frustrated when it takes a few weekends.
