Any sources for pipe swaging?

I'm trying to build a set of headers for my Nailhead powered 39 Chevy pick up. I have a set of laser cut flanges but I need some direction on swaging round tube to fit the rectangular ports on the flanges. Any ideas? Thanks, SpeedCity

 

What I have done in the past is to fit the round tube into the square hole and tack into place and slowly and carefully work the round tube into the corners with a ball pein hammer, a good body hammer can be helpful. It may sound crude, but if you take your time it will work. Try not to move too much material at a time as this will thin the material as you stretch it making it prone to cracking. Another technique I have used is to have an aluminum plug made that is just smaller than the port size plus the wall thickness of the tubing that tapers down to just smaller than the i.d. of your round tubing and pound away.
I hope this helps.

 

Vise and hammer...squish it til it fits the flange hole, tack weld it in place, hammer it from inside the tube to fit the flange, weld the tube and flange and you're done...

 

I would use smaller tubing that will fit into the flange and open the other end to slip into the tubing . Stretch the tubing going through the flange,its like a step header. Hope this helps ,

 

Thanks to all for your suggestions. I was thinking that I could build an expanding mandrel set but I was hoping that someone already had done it. I'll try the hammer and vise routine if all else fails.

 

I made a swaging die to do that for a set of "Y" Block Ford headers. The flange plates had rectangular holes. I made the tool to change one end of short pieces from round to rectangular-the flanges now have about 1 1/2" of 1 5/8" round tube sticking out of them. Our plan is to slip 1 3/4" header tubes over the short stubs and weld them in place. If any of this would be helpful, I'm in Indy.