Lots of old threads about them and lots to learn . I bought a 04 tc45 a year ago and researched the **** out of them . The d's are older than the da's . D's have very thick fiberglass sheet metal. DA's went to plastic and were prone to cracking by the fenders. D's have a screened vent on top of the hood better looking head lights, DA's moved the battery location. Tc45d's have no mid pto TC40d's do,TC45da' do.
If you are really interested defiantly do the research. Mine is a cream puff everyone thinks it's a brand-new tractor runs great. No electronics. no pollution crap.