Quick and easy...I have 66 smithing, need 70. I have enough sc hammers for the last 230k xp or so. Whats the cheapest/best to smith? Ive heard mith arrow heads but do they sell?

You can try bolts, they usually sell pretty decently, I'd really doubt mith arrow heads sell, at a decent rate anyways.

iron platebodies can be deceptively look

and will probably sell well before the bonus xp weekend

 

still, i recommend saving those SC hammers for something better, and smelting gold ore until then (superheat or furnace, both are pretty good)