I do not know the person you posted the link for.
I would try these places -
Dan Cragin
www.dcperformance.com - I bought a complete 3:54 rear end from him, and never looked back.
Unitrax - They build a lot of rear ends, and seem to be the preferred vendor to buy gears from.
www.gounitrax.com
Valaya Racing (408-448-8811) Ted has done a TON of rear gear conversions, and may have something for you in stock.