Most common lifeline wire size is 7x7 3/16 x 5/16. 7x7 refers to arrangement of strands in the wire rope. 3/16" is the wire diameter, 5/16" is the wire with vinyl coating's diameter. It's now up to you to contact whomever you plan to purchase the hardware from to determine what exactly you need. First question is what type of connector is on you wire. Is it a threaded stud? Are the threads the same orientation on both sides, or does oneside tighten clockwise while the other is reversed. If so you'll have to buy the appropriate hook for the reverse. If you choose to buy a kit, such as made by suncor, be aware you will have to purchase a special compression tool, the simple ones run about 40-50 bucks. You can cut the wire a hacksaw and some tape to discourage fraying.
I encourage you to research this subject by visiting a few online chandlery's such as west marine, velas sailing, Defender, etc. You'll learn a lot. May save some money, if you do. I replaced all lifelines, fixtures, stanchions a few years back and I saved quite a bit by schooling myself before ordering anything. I found the best deal at San Diego Marine's cruising division called "downwind marine" Good luck.