You won't find a 200 block in a transit, these are mostly 202, which are just a different deck height 205, the 200 is MUCH stronger but if std power is all you want, a 205 is fine, just make sure it is bored with a deck plate on, as they distort like crazy when bored otherwise.
I'd certainly be happy to use a 205 at 450bhp.
As said Matt Lewis for bits.
tabetha