> And now I am hearing the studs may need replaced by
>longer Studs? 

WRONG.

People, listen here - 
I have no Idea why Cory said that but NO you DO NOT have to replace the rear
studs to mount the "Carat" factory alloys.

> Does anyone know of an after-market source (or any cheaper
>source of factory parts)? And will the lugs from the steel wheels fit (or not)
>temporarily while I purchase one wheel a month for four months?

Porsche 914 alloy lug bolts will fit the fronts
Audi 5000 lug bolts will fit  fronts(even thought they have a rounded taper
under the head)
these should suffice, but it would be in your best interest to go back to the
salvage yard and look on the ground around the van, as they may still be laying
in the dirt. 
 as for the rears, I'm sure you can get the lug nuts to grab onto the studs a
little bit, but it would be safer to do it right. 

Try it and see what happens. But for safety's sake - don't do it if it looks
like it won't work. Every set of Carat's I've had, I've always had the lugs - so
I'm not totally sure how the rears will work. 

chris