The original may not always be the best - for example I replaced the mainsheet on my 33 with larger diameter. the blocks were big enough. Also the length was far too long. expect you will find most halyards are 12mm and sheets 14mm. reefing lines may well be 10mm, but some people replace them with dyneema 8mm.
I buy my ropes either as reel ends if the length is ok, or 100m reels and make up to length using halyard knots rather than splices. This can be as much as 50% cheaper than having halyards with eye splices made to length.