Im with the torch guys. Impact is by far the quickest when things are not worn out and rounded. Ive cut lots of pads with the torch ,thru the link and cut the bolt head . Plasmas are great but the tip or head is too big and you cant wash a bolt off like a torch the plasma just burns anything metal in its way including your pad or rail. A big dirty tip on a torch ,get things nice and warm ,start your burn and pull the torch back a bit and keep burning . with practice you wont touch your base metal at all. Dont run too much oxygen pressure 40 psi is good, go easy on the oxy trigger on your torch just feather it and start on an edge that will heat quick, you can hold the tip back 3/4" or so and keep a nice wash going . with lots of practice you can wash the nuts off bolts that you really need to save with out hurting the threads, this is an important skill when your out in the bush in the middle of the night trying to make something run for the morning. By the time you get done with your pads you will be good at it. One final thing use oxy acetylene ,it works better than propane on this kind of burning than propane.