Funny, I'm in the middle of doing this right now on my Cuda on the cheap... Done it many times on other cars. I simply took the battery tray from the engine compartment and mounted it to the trunk floor on the right side. Then used the stock hold downs (had to make an extension for one of them). Connected the negative cable to the mounting bolts (after cleaning up the paint). Going to Lowes tomorrow who has 1, 2, and 4 gage stranded wire in stock and sell by the foot. MUCH less expensive than the kits or summit/jegs. I'm thinking I'm going to run the positive cable from the battery under the car and up the tunnel. Then connect directly to the starter. I hear people talking about running the ignition wires as well. Actually, you don't have to. Simply run a wire from the starter terminal post with the battery cable up to the solenoid where the old + cable connected. This provides power to the car and solenoid. Works every time. I also run the alternator output wire to that same battery terminal on the starter. Electrically it's the same as stock.
Derrick