We do this all the time...we either relocate batteries or install additional battery/ies to other parts of the vehicle.

What you need is the following;

Good quality OFC 50mm2 (0gauge) cable from front to back for the positive
You can add either 1 or 2 fuses depending on how safe you want to be...1 fuse as close to the battery as possible is sufficient. If you want to add two, you can add 1 near the front bulkhead
With the earth, as stated above, you can uprate the front earthing points to 0g cable as well - uprate the engine to chassis cable as well. Or you can run a new 0g cable from the battery direct to an earthing point in the engine bay. As well as this, I would also earth out the rear battery to the chassis right next to it.

Ill be doing the same into an Orion soon, and the plan for that is to put the battery in the boot, extend the current cables from the engine bay area to the boot. Run 2 0g positive cables from battery to engine bay...one going direct to the alternator, and one going to the starter. A third 4g cable run will be made to connect all the cables that will normally run to the car loom. A 0g earth will go from battery to chassis point in engine bay, uprated engine to chassis earth, and the battery will be grounded to a earth point in the boot.

If you need any help or info...just drop me a PM