Hey Tim, what size tube do you want to use?
I think you will find it easier to build with new tube as secondhand 4 stroke headers are bastards to weld due to the carbon buildup inside, unhealthy as well.
I have bends in...
1 1/2" OD,
1 3/4" OD,
2" OD
large radius 1 1/2" OD bends
& can get some other sizes like 1 5/8" or 1 3/8"