Lincoln's a great brand, but according to Sears it only goes up to 1/8".
My kit bumper from 4x4 Labs was all 1/4". That would do it, but you would have to grind out all of the joints at an angle and do multiple passes (like 3+). On both sides. In a word......slow.
My buzz box did it in single passes, and I had it turned up less than half of the way. I've severed quarter inch steel with it (nice option with the more powerful arc welders), and didn't even crank it up all the way.
Ideally you'd want something that can do more than what you'll ever need. Look for something that can do quarter inch, minimum.
This one will do quarter inch for what you want to pay.
This one would be better.
This is what I have. I like how they say "
Welds metals 16 gauge......and heavier."
I found that on Craigslist, lightly used, for $100.