exhaust ed need WHY pipe

In order to get the Suburban going I need exhaust. But the Y pipe that came on the 360 native to this car will not work on a 318 due to taller block of 360. I've checked e bay out, no new ones and money for a dual exhaust is not in immediate future. Does anyone know a parts store that has real old stock. I can come up with a part number as I have a old Maremont catalog .
Or dual exhaust head pipes (not available with a 318).
Author: 73 suburban