It looks like you got your answer about all rope halyards, at least for 5/16 sheaves.
No wire to rope splices for me. Mine has a SS thimble using a nicro press. I have the rope halyard tied to the thimble, but plan to change it to a braid /braid splice around the thimble.
Take Jumaggafanny up on his offer for advise. He has done some amazing things to his Helms 25 with excellent picture documentation.
Rehoboth Bay/Indian River, DE
S/Y KJ, Helms 25