I have a silent choice exhaust for sale, recently removed from a 454. I believe it will fit other chevy blocks as well. Comes with all the parts and works perfect. It's the air actuated version, pump and cylinders are in great shape. Can send a pic upon request. There are two for sale on ebay for $600, I'm open to offers.

You might want to move this to the for sale forum. It might sale faster if somebody is looking to buy.