It really depends on the size of the jumper cables. Jumper cables can be anywhere from 10 guage to 2 guage for a really good set.
12 volt starting usually requires 4 guage to 2 guage wire depending on distance.
6 volt starting requires 2/0 cable, not to be confused with 2 guage wire which is much smaller. Don't forget about grounding the block, chasis, and cab.
