Originally posted by Jeff_99gs
The tube should be as large as you can fit. Which is about the sizes Matt just said above. I will confirm this and get back to you. The only problem with this is finding a machine shop that will weld steel tube to cast iron. I'm not a welder, but apparently it is not the easiest thing to do.

I did it myself, the tube I used was 1.25 ID. Its all I could find. I cut the stock 02 housing and welded the tube on myself at work.
To weld steel to cast you have to use 99% nickel welding rod with an arc (stick) welder. The weld is gonna be ugly but it holds. If you use normal mild steel rod or a MIG welder the weld will crack. Ill have to try and take a few pics of it installed tonight and post em up. You really cant see it when its installed though.


Here is a pic basically of what I did, Mine isnt as pretty as this job though. I dont remember where i found this pic, but its from a shop that does it and sells it. I saved it so I would have somewhere to go off of.