The 250 is very simple and easy to work on. The 4200 much more complicated to install and is computer controlled. A lot has to change in order to use it. I too would like to change to this engine when the time comes. It would be a huge project for me though, so until this current 235 wears out I will just be investigating the possibilities. At the very least my whole drive train would have to be replaced. EFI_DIY has put one of these in IIRC.
