I don't believe you can change the drawing origins for item numbers on a per prodcut basis.
However, you can change the "item numbers" file - it is called "ItemSymbol3D.dwg", located in your UserFiles folder. It is a simple AutoCAD file. We rotated our item number tag 90 degrees "up" (from the right side view) so that it can be used in the Elevation drawings, then moved it up 18" and forward 16". All from the 0,0,0 point, of course. This places the tag up and in front of 90% of our products.
Play around with it and find your best settings. t's immediate, so save the file, open one of your MV drawings and re-draw a product.
If there's a way to place the tag on a per-product basis, I'd love to know about it! 
Wm