I'm not sure what you are saying. You said know your width, but also to measure the 180 loafer from heel to the tip of the toe? What good is that in helping you to determine what other lasts/models from other brands will fit you?
You need to know the length of your foot and the width, and if you can, the height of your arch if you have a high instep. These numbers are useful because you can send them to the company, whichever company that may be, and they can suggest lasts, size, and width that will fit your foot best. This goes for "pointy" loafers as well. In fact, it goes for all shoes. However, loafers are tricky compared to shoes with laces or buckles for obvious reasons.
This was my attempt to give a tip on how to size 180 westons based on how I did it. Everyone should know their width size beforehand. The thing to know its the outsole measurement from heel to toe. I used the most similar loafer shape I had with me and used that as a reference. Then I ask for the outsole measurement of the 180 loafer before buying. And this method can work for other lasts like mentioned.