VIN-Trader

Brand new to the Forum so forgive me if I mess up. Have a cousin, non-technical, asking me to find replacement exhaust pieces for his Roadmaster. He sent me the part numbers and pics. Front 1288764 and rear 1288765. Have another part number 1390880. The last part is the heat-riser? Anyway, looking at what I can find, it seems the manifold is a three piece assembly. Then it looks like a 4th piece is mounted as a heat-riser and exhaust exits through the bottom. Let me know if I am right and part numbers for all. Looking to buy the whole shooting match.