You will need to get the tank out of the vehicle if you are going to weld the bracket on. I would not want to even cut off the old bracket with the fuel tank right next to it.
As far as the front bracket goes, I cut off my loop then got the front bracket in and welded up. I wanted to make sure it was going to clear the bracket, clear the control arms and clear the driveshaft with plenty of space to allow for articulation.
It did kind of suck to get this loop back in and hooked up. What I ended up doing was to get a piece of tailpipe and cut 2 small sections at the correct angles on one end. Weld on the ends to make up the weird angles needed and then use those flat band clamps on each end to make up the joints. I cut out my factory joint so I wanted to be able to remove the exhaust loop from the cat if I needed to do work later on. Plus there was no way I could see to weld the pipe all the way around with a MIG welder. A TIG with a short tungsten and cap may have been able to get it but not my set up. The band clamps made it real easy to hook up.
In the photos I posted on page 2 you can see several views of what I am talking about. The tube from a paper towel roll is almost the right size to use for the mock up.
I almost said forget it and go to a flex pipe or something, but after reading several posts about how our engines need this pipe I decided to do it right. Sure feel better about it to.
This part must have taken me a full day to get it right. I would love to see in person how the guys at Offroad Evolution do it. Bet they would laugh at my crazy ass way of Git-n-er done. Oh well it worked and its done.