What size wire for the through wire is best,and I take it it should be stainless.

Try www.njtackle.com

just go to the local welding supply and get 308L welding wire. Cheap and strong

It can be found on eBay for around 41 bux for 10#. shipping included

be CAREFUL what you get for wire on ebay...I got 100 lbs of 308 wire that is so brittle you can't bend it more than 25 degrees without it snapping...it was advertised as er308l too....

which is better?

308L
or
316L

which is perfered in making larger plugs 1/8 or 5/32?

i would think 1/16 is too thin but what do i know...

308 is easier to bend, .062 or smaller is fine depending on size of plug.

I got 10# and it is great stuff. 1/16" or .062 is plenty. The larger stuff 1/8" or bigger if ya are targeting giant blue fins.