Easiest and Cheapest way to replace Catalytic Converter?
 

My 2000 LT 4x4 4DR has the "Rattling Cat" issue. Throwing the 420 code for the O2 sensor now. I'm wondering if there is an easy way to put a new one in. I don't have a welder. Wondering if I can just cut the old one out, and use adapters and clamps to put in a new one? Or do I buy the whole thing, Y pipes and cat to the muffler flange and bolt that in?

I'm sure this was caused by the spider injector leaking previously, but it has been replaced with the MFI style now.

You can put in universal cats, but typically they are welded in. My advice, let an independent muffler shop do it. It's a very simple thing for them and not worth your trouble. You can shop around. I'm sure it's competitive. Don't go to Midas or any franchise shop unless you want to pay a lot.

Suggest replacing the pre-cat at the same time; it is the smaller "bulge" in the Y-pipe. I got a replacement Y-pipe and did it myself. I sawed the old one and it came out in two pieces however the new one required lowering a cross member to get it in. Used a clamp at the joint and new bolts ( really rusty, corroded) at the exhaust manifolds. Took about an hour or so to do.
Getting to the exhaust manifold bolts requires some extensions, impact sockets, hammer, penetrating oil, cold engine.

Have fun.

If I remember correct, only the California emissions vehicles came with the pre cat, so his may not have it

Yeah, Midas said about 350. The other local places weren't much less, I think because of the labor to take the crossmember down. I think I have a plan. Ordered a cat and an adapter extension pipe that I know will work well in front of the cat when I cut it the right length. Might be interesting behind it adapting it to the pipe, but I'm just going to have to figure it out when I get the old one out. If I can save 200 bucks and do it myself, I will. If I need to weld it, I can borrow a welder from a buddy and give it a shot. Just been a long time since I did any welding.

Yeah, that looks like a lot of fun to drop that crossmember. My bolts for that are really rusty. Would like to avoid that if I can. Mine doesn't have a pre-cat. Has been a MN rig its whole life.

I did my Y a couple of weeks back. The top bolts of the flange to the manifold was the most difficult part. You do have to lower the crossmember. I was able to get it in without dropping it. Nice not to have the death rattle from the old cat. Since my exhaust was welded to the y, I ended up replacing everything manifold back. Just a lot of time on your back. I dream of a lift. Mine was a Midwestern truck, so plenty of rusted bolts.