chines1 posted:Windshield, doors, top frame are all that is "required" to make the change from speedy to D. While that may sound simple, there are a LOT of variables in play and sourcing all of the parts is not only difficult but VERY expensive to do properly.
I asked a similar question to Henry once, but going from D to Speedster. I got the same reply - that it was almost impossible to do the switch, and certainly expensive if it could be done.