Have you done any of these conversions yet yourself? That would give you a pretty good idea of the cost & complexities involved.
You can research EV conversion costs fairly comprehensively by studying the data in the EV Album:
EV Photo Album: Our Electric Cars on the Web
There is likely a lot of information available to the Googler about bio-diesel conversions available as well, since those kits are commercially available already and lots of people have documented their own conversions.