Hello Laurence, welcome to allmetalshaping. The aluminium body that Ron Covel builds is not a T body, the model T was steel. You would have a lot of difficulty making a steel body the way he shows. You do not really need a buck to build a Ford body of that era, at least not a full body buck, especially if you have an original to copy.
Ford bodies of that era are made from lots of smaller panels fitted together on a subframe so the way to restore or reproduce one is in the same way. Many of your existing panels would give you the information to produce a proper replacement part, some could be even be re-used.
Here is a link to my '27 T build on here.
http://www.allmetalshaping.com/showt...hp?t=5469David