Yeah, it's cheap as hell to weld it up, but it's not the steel that's the problem on the pre 2000 models. It's a design flaw in how the manifold was made. It can't hand the expansion and contraction that it's put under. Replacing it to a newer style model with the expansion joints on the 1 and 6 tubes is the way to go.
And honestly you don't have to spend a ton of money on it. Do a search for 4.0L Exhaust Manifold on Ebay. Grab yourself the 75 dollar one and slap it on. I've had one on for well over a year now and have had no problems at all with it.