Wes:  I know that this doesn't exactly answer your question about LED's but
I just got through looking all over for the instrument light and air vent
lighting bulbs and sockets and have published my findings on my site.

Take a look at
http://www.weidefamily.net/vanagon/

go to
Electrical > Inside Lights > Dash & Instrument Lights

It looks as if the LED site you mentioned does have some LED's that will
plug right into our sockets, at least for the instrument lighting. I've
read that some folks are not happy with the fact that the LED's
don't "flood" light as much as "spot" it.

Thanks,
Brent