A hacksaw. If they are that bad, replace them. You probably have rust on the inside of the lines if they are that bad on the outside. You can make your own or buy prebent stainless steel from a vendor like Classic tube. I was very happy with there product. the Stainless steel are great, but you can't make them, you can't make the flares. You could buy tubing from whetneys and bend your own. I tried that and wound up buying from Classic tube.
65 Fastback,289,holley 1850,Edlelbrock performer 289,Power heads,T-5 z series,8"2.80 rear,Canadian Mustang "Real Big Kit",Fuel Safe fuel cell,70 highback seats,SSB dual MC front disks, Stainless steel brakelines,pertronix points/coil,3 row radiator.