I've used 3/8" copper tubing to splice battery cables in a pinch--you can smash it flat with a hammer after inserting the cables and if desired,solder it too,with a propane torch...keep in mind this is a crude "fix" not intended for permanent use,but it'll last a long time..harder still is to re-insulate the tubing with something so it wont short out to ground if its the positive cable--heater hose or heat shrink tubing,or lots of electrical tape works ..
I had a lot of no-crank issues with my 72 K5 even after I put in a push button to activate the solenoid (thinking my ignition switch may have been bad in the "crank" position)...sometimes it still just "clunked" or spun over a few times and would quit,then nothing..
One day it refused to start so I crawled under the truck to jump the solenoid with a screwdriver,and I got nothing but some weak sparks..so I rolled the truck down an incline,and popped the clutch with the key "on" to start it...while driving it home,everything went dead..no lights,no radio,no cranking,it was like the battery was missing..
I spent a half hour crawling around under the truck looking for burnt or disconnected wires,found none..as a last resort I decided to take the battery cables off and clean them and the terminals--when I pulled on the positive one to be able to get at it better (it was so short it barely reached the battery),I discovered a large lump of tape on the cable where it went under the battery box..
I unwrapped all the tape and what looked like baking powder came out,all the wires were corroded away,except a few strands!..soimeone simply hacked the old side post end off the cable and "spliced" a top post one to it --by twisting the wires together,and just taping the snot out of it!...
I had jumper cables with me,so I used one to hook the battery positive post to the starter where the cable went to the solenoid,and it cranked right up and ran--next day I replaced that cable ,and noticed everything now worked a lot better--starter spun faster,the lights were brighter at night,even the radio had less static and better bass..
New cables are always better--factory ones often are a combo of copper and aluminum,which isn't as good as a conductor than all copper is...and if someone hacked two cables together,the splice will likely be all gangrene and corroded after a year or so..