summit-racing.com if you want to keep battery, get a sealed box kit.
I have a yellow top optima battery which is gel filled so ok to be inside car. it is held down with threaded rods on drivers side in boot welded in place. a plate between the 2 holding it in place.
The earth/negative connection from the battery is straight onto the threaded rod earthing up the metal work
The live is off the battery to a 150amp inline fuse and then runs straight to the engine bay, and terminates straight onto the starter motor, the fusebox feed in the engine bay is also lugged onto the starter motor.
I used the biggest amp cable i could find.
If you need some picks i will post them up to try and make more sence.
2.5 Ze straight neck, blitz intake, mazdaspeed engine mounts, fidenza flywheel, CM II Clutch, KL-36 ecu, Magnecor 8mm Leads, Battery Relocation. Hotshot headers, 2.5 mandrel bent stainless exhaust, hi-flow cat, Speed hut dials, custom coilover set up. Custom willwood big brake conversion.