I found something on ebay that might help out in your search for perches. This auction is for a 10 bolt housing with what looks like multi leaf perches. The seller would probably cut the tubes and send the perches to you and scrap the rear axle housing. If the perches are correct for your axle it is worth a try.
http://www.ebay.com/itm/1970-81-Cama...50&vxp=mtr The price is hard to beat and its close to you. I have a pair of perches but they were welded onto a '69 Chevelle rear end so it would be a major job to get the excessive welds cleaned up. Clint