several things to keep in mind. use good cable. had a 71 torino 429 with ~11-1 compression. guy i bought it from moved the battery to the trunk, and used standard bolt down kit. if i was running errands and had to start several times in a row the cables woud get too hot and i couldn't start the car. had to carry jumpers areonud. jump from the trunk to the starter relay and it would start ok. ran a new 2/O cable for the hot, jumpered the original cable together and never had another problem.
2ga might work, but would suggest 1/O, maybe even 2/O depending on motor, electric fan, stereo... use WELDING cable. will be fine strand with rubber oil/grease resistant jacket. super flexible. worth the extra $$$. use the correct crimp on lugs fo a specific size cable, not just some generic ones. go to the electric supply house and ask them. t&b, and rand are some of the better ones.
2nd thing: use a cut out switch in the trunk right next to the battery. if you ever pinch a cable and ground it out it really sucks trying to find a wrench to remove the battery cable. also end up with burned fingers. trust me on this one, i know. also works as a security device, especially if you get one that requires a key. can cut juice to the whole car, and crooks have to figure out what you did before they can drive off. mine went through a monster relay. had a small toggle switch in car that killed the relay in the trunk.
3rd thing: use a junction block in the engine bay. run the cable from the trunk to the juncion block. connect from the junction block as if it was the battery. if you ever have to jump the car you will be glad you did. also makes a good point to wire in your new relays for your head lights.
4th: use a non venting battery (optima or panther), or a vented marine style vented battery box. torino's voltage regulator stuck one day. battery overcharged and started off gassing. almost passed out before i figured out what was going on. installed new voltage regulator, and plastic battery box with vent tube running out through gas filer area. trunk doesn't look like it, but it is part of the passenger compartment.
just a few thoughts.