Thanks, Pete! Y'know, I've got a really great old Millermatic 35, been welding for 40 years, and my downpipe came out SOOooo ugly ha haha! Some days ya got it, and some days?
I couldn't find the part I needed because I was looking for a 3" to 4"
ADAPTER, then I remembered 'plumbing' is different. I typed in 4" to 3"
REDUCER in search and there it was! Instead of a long taper it's a no-transition reduction from 4" to 3".
http://www.supertruckusa.com/products/77620_962.htm
Price is right, and I hope it's a heavy enough wall thickness. This is not the 'adapter' that I mentioned above, but a different part.