What is the tolerance and finish on the laser cut parts? Front bushings would be nominally 1/4" thick, and rears about 1/2", perhaps a little more if the wheel centers are much more than 1/4" each.
Would they then need truing up to size on a lathe? I think you want a pretty good precise fit, at least I would.
Another option is
http://www.warricktubing.com/I bought a piece of seamless steel tube listed as 4.75" ID and 5.25" OD from them last year along with some stuff for another job. I have not really measured or checked it out to see if close enough fit to just cut off slices of it or if needs a little machine work, or if there is even enough material to machine.. If not then you could buy from them a somewhat oversize tube to turn and bore to what you need. Might be cheaper and I'd think a lot easier than starting with a solid bar or burnt out rings.
Grigg
