Folks, I need a bit of help here. I measured the stem I pulled out of my 84 pinarello and it looks to be a 3/4" stem, but when I look at sheldon brown and other places they dont list a 3/4 stem, or list it as relatively obselete... I am looking to buy a adapter to use new stems on this bike, and not sure which to buy, they have 1" and 1 1/8". What say you all?

here is the adaptor: https://www.nashbar.com/bikes/Product...1_10000_201527

You don't have a 3/4" stem, you have a 7/8" stem (22.2mm), which goes into a 1" steerer. So you would want the 1" model. And if you look around those can usually be had for about $10. {search quill stem adapter}

(shill time) Niagara Cycle has an Origin8 for $9.33