My 1000# molly mule uses 000 shoes.
Sounds like i'm screwed
Maybe not. I use 000 and is mule is maybe 800 #'s , but usually have to shorten the heels. Go to the Cavallo web site.They have charts there to decide what size you need. Width at widest part of the hoof and length from heel to toe.
Call them and if they specify the size you need and they don't fit, they will pay for shipping back and give full refund, if they are still clean and in new condition for resale. You give the the measurements, take a set of photos of the hoof and send it to them.Instead of just ordering a pair yourself. Be sure to measure after a fresh trim.
They have a Slim Size that fits mules better.
https://cavallo-inc.com/things-to-know/how-to-measure/