Using the body from a 300TE is definitely doable, but beware of the DMV! In many states, you are going to have a TOUGH time explaining to the DMV that you have a diesel engine in a former gas engine body. California, for example, do not need emission tests for diesels but required for gas engines. Well, the VIN plates and other IDs from your rusted body could mysteriously "moved" to the new body. That will save you a lot of headaches.