[Terry, NJ]

Dear Scott, Too bad it's not a Briggs. I'm making Briggs door wood right now and I could give you a few pointers. Are you sure it's ALL rotted away? Even small pieces can give you a dimension or two. Or you can buy two of the kits(Front and rear) and duplicate as a mirror image, the other side. If you're patient, you can "Develope" most of the dimensions. For instance. You will notice that the inside of the doors are smaller than the outside, only the sides and bottom of the doors. This taper is about 2-3 deg.
But it means you'll have to set your Table saw blade on a 2-3deg. angle AFTER you make the piece. BTW, I've developed the height (Or length) of the door, on my Briggs Town sedan to be 40 1/2 inches. It's too bad you're not closer to Pa. I could provide you with a plank of Ash for $35, from which you could get all four (It is four isn't it?) doors. Ash is what Henry used, also walnut, beech and other woods. For equipment, you'll need a powerful table saw, 10 in. dia. capacity.( I use an old Grizzly that I found,1 1/2 HP. Don't use a saw like a modern sears, you'll burn out the motor) a drill press w/ 1/2 " chuck. a belt Sander. An angle gauge, a GOOD 6' scale, a GOOD adjustable 12" square. A 24 " scale and a vernier caliper and lot's of patience. If you don't have all of these sitting around, they are available at your local flea markets for a minimal cost.
Post your problems as you go, we'll try to answer them for you.
Terry