Your selection all depends on what the wire connection to the mast configuration is.
Most 'good' riggers will use a swaged eye connection for the upper mast to wire connection ... (if thats possible), replace the closed 'barrel' turnbuckle with an 'open frame' type, etc.
The bottom connection to replace the 5/8" T bolt should involve using a 1/2" Ø forged T-bolt connected to strap eyes ... the proper sized 1/2 strap eye, and not a 1/2 Tbolt assembled to a 5/8" strap eye to minimize 'flex' for 'fatigue' purposes. If you use a 1/2" Tbolt on a 5/8" strap eye the strap eye will unduly 'flex' and will lead to short life and fatigue.
I 'believe' that you can use both 5/16 or 3/8 wire in the Norseman ... all depends on the size of the insert. However, you have a WS 32, built probably in the mid 1980s or earlier and if there are Norseman fittings used, it means that someone cut away swaged connections and added the Norseman to the then 'old' wire. Your OEM rigging is at least 15-25 years old ..... and if you plan to sail this boat hard and long I'd recommend that at least the capshrouds, BOBSTAY, headstay and backstay be entirely replaced with *all* new ...
On a cutter rig If you lose a bobstay, the whole damn rig comes down. If that lower bobstay connector is those damned machined together T-bolts and with the constant dipping of that lower connection continually into salt water .... the lower bobstay connection WILL be the connection in the most vulnerable condition for 'failure' .... check out that BOBSTAY and its connections, first. If the bobstay and its connections are 'shot', also remove/inspect/replace the BOW-EYE fitting ... any visual sign of 'rust weepage' on a bobstay means ---- crevice corrosion .... "warning Will Robinson, warning, warning".
.... and then there are the chainplates.
Check the bowsprit's cranse collar for fatigue cracks especially near any of the 'welded on' lugs ... take it off and take it to an 'automotive machine shop' or machine shop that does specialty stainless steel fabrication ... and have it 'magnafluxed' to insure that this vital rigging component is still 'healthy'. Any localized 'dulling' of the surface on a cranse and near any 'weld affected zone', usually means that the cranse has 'crystalized' and is getting ready to 'fall apart' from fatigue. If the cranse needs to be replaced, PM me and I will supply a dwg. of a much better FATIGUE RESISTANT design.
I 'think' the rigging on the WS32 was well overbuilt ... with a safety factor of 4:1 using 14,000 psi wire .... so that wire and rigging fatigue is well lessened. Nevertheless, in the very fine print of most insurance policies nowadays, youll find to keep the policy in effect ... "rigging entirely changed out every 10-12 years OR rigging failure and consequential damages are excluded and not covered ... .
Get an experienced rigger who actually races sailboats or who actually sails long distances ... many dont and then simply dont KNOW what to look for.
Replace the most vulnerable first in sequence if youre on a tight budget: bobstay -->, Head & backstays, --> caps shrouds ... --> then forestay and aux. lowers, and 'finally' the intermediate stays (or replace or them with amsteel/dyneema running backstays).
Your WS can easily sail in F9-10 conditions and survive .. IF the rigging is intact.
What was the name of this boat when you bought her? If the boat's name was "East Snai" with homeport of NYC" ... PM me.
;-)
