Cartridge Alignment

You can get a Geodisc on Amazon for $49.95. They work great.

I second the Geodisc recommendation!

I recommend the Mint as well.

That being said, vinyl engine has some free downloadable protractors for the Thorens on their site. I'm not sure exactly were though.

The Mint is just outside of my range due to repairing a Quad ESL. I thought initially that I could purchase a Dr. Feickert protractor but that was before I arched a speaker panel.
I've read in many places that the Geodisc just roughed in the null points but doesn't have it right on. Any thoughts about this?

I believe that your Grado mono cartridge will have a conical stylus. If my assumption is correct, cartridge alignment is a non-issue for you, as in it doesn't matter at all. This is because the perfectly round cross sectional profile of a cone will sit in the grove symmetrically at all points along the arc of contact between the stylus and the record. Put another way a conical stylus is always "aligned" in the record groove. Cartridge alignment becomes critical if the stylus is elliptical or a more complex shape. Alignment is only achieved at two points along the arc of contact and optimizing (or minimizing) the error at other points is what alignment is all about. The MintLP alignment gauge is superior to all others because it is the only one on the market at any price that addresses the problem of parallax. It is set up for the Stevenson algorithm, however, which may or may not be the one you want. I like it and strongly recommend the MintLP. But again, it is doubtful you will need it.