welding them in would be easier than having the shop fab and install flanges to bolt everything together. although, it depends on wether or not you plan on swapping an O/R midpipe for a catted one for emissions testing. if so then bolting would be the way to go.01mineralgrey6 said:the old mufflers have to be cut out, then the new ones are normally welded in but you can bolt them up with clamps. I would just take it to a place that does exhaust work, and have them welded in. Oh and you would need hangers for the new mufflers.