My father install the last muffler on my truck, and it lasted for close to 150 000 km with only two peices of wire and some factory clamps =) Sure it swung around a bit, but it was as secure as needed for highway driving. For my current muffler that I just installed, I took the muffler and brazed some steel roofing straps along the bottom and just bolted it to the frame then clamped the fittings with some good clamps. I used the factory piping as it was still good, just needed to replace the muffler and generally tighten things up in it. Sounds great, and that muffler is in there tight, it hardly moves anymore. Total money spent? $78.90 on two clamps and the muffler
Its easy to do, and cheap if you do it yourself with some improvising!