John Thompson books and plans are good I have a monmouthshire waggon on the go at the moment which I am working with plans and his book "Making Model Horse Drawn Vehicles" which covers Haywain, Pony and trap and a farm waggon. It also contains some useful information on some of the construction especially the wheel type and how to make them.
Mine is made from Oak and the mortice and tenons are all cut. The mortices are just big enought to be able to file them out with a flat needle file