Figuring out girth size...

Hello! I am headed to the used tack shop today and all I have to go on to figure out a large pony’s English saddle girth size is her chest circumference. I am only picking up a few things on trial so no big expense but I didn’t want to be totally wrong and not be able to get her saddled on Sunday. Her chest is 73” and she is a draft cross 14h pony. Anyone have a similar chested pony that could help me out? Just a Range is what I am looking for so I can pick up a few girths in that range and try them out. Thanks in advance!!!

I’d run a string from the middle hole of each billet to the middle hole of billet on the opposite side, measure it, and subtract 2" if there is elastic on the girth you’re interested in…3" if there is elastic on both ends of the girth.