exhaust Y pipe

Did they even make a y-pipe that would fit the 340 exhaust manifolds?

340's all came with dual exhaust and I believe that the outlets for the 340 manifolds are different than the 318 manifolds.

Why would you want to run a single exhaust on a 340 or 360 anyway. Single exhaust is restrictive and will choke it back some. Dual exhaust will let it run better. Why not just go with dual 2 1/4" exhaust?