>how different are the offsets? since some machining is required are the
>offsets different or is the width/height of the rim different..

It bolts right on. The ONLY machining done to the wheel is the center hole - and
that is machined out to clear the axle hub grease cap on the FRONT wheels. The
rear wheels will bolt on fine without any machining, but I usually machine all
for to ease in rotating the tires. 

As I said before, you'll need a thin wheels spacer on the FRONT ONLY to keep the
wheels from rubbing against the XXX (i have to check on the name of this part)
though, it could be ground off a little, and eliminate the need for a spacer.  I
have seen it done both ways. 

No spacers or grinding needs to be done on the rears, they sit right up flush
against the drum.

>also, are these available in 14" with the correct bolt pattern?

Nope.

I prefer the 15"s anyway - if you run 205 60 15's, then the van sits at the
exact same height as a regular 14" Vanagon wheel & tire. 

If you run 65's, and 70's  - then the height of road clearance will increase,
without any rubbing. 

chris