It all hinges on whether you need to comply with emissions. If not, there are prebent dual kits. but most of them are meant for headers. If you need to hook up to stock manifolds, some creative work is required. Heartthrob Exhuast (made in the USA) sells a dual kit for the 70-81 Camaro that might be a place to start. https://www.autoaccessoriesgarage.com/Exhaust/Heartthrob-Exhaust-System/_Item/_229900008. Here is their instruction kit http://heartthrobexhaust.com/8144710.PDF. You still need to modify your crossmember for the driver's side pipe. Jegs and Summit sell dual-hump crossmembers for their dual kits for G-bodies.
