Howdy:
All exhaust manifolds from 1960 144s to the last of the 200s in the eighties. are interchangeable. There weree differences in the manifolds through the years, but all are interchangeable. The earliest engines, from 1960 to 1962 had a 1 3/4" outlet and used a flat gasket. They were prone to cracking. 1963 and later manifold have a 2" outlet and use a donut/firewall type connection to the head pipe. Exhaust manifolds varied slightly in internal volume over the years, but there is only conjecture as to whether is is a flow advantage or not. Later manifolds do have more metal in them, strenghtening and reinforcing problem areas. The larger internal volumes tend to be later 1978 to 1982, but these have extra bungs and taps cast and machined into them that must be plugged. It is my contention that these irregular shapes do not aid exhaust flow.
Exhaust manifold with the same casting code, whether on a 200 or a 250 appear to be identical. I am not aware of any evidence that a 250 exhaust manifold is capable of better flow than a 200 manifold, regardless of year. I have heard this before and looked at a bunch of Econolines and 250 engines but have not found this to be true.
64 200 ranchero, if you know of some proof or evidence to support the thought that a 250 manifold will have "Better flow" than a 200 please share it with me. I'm willing to learn.
My choice in exhaust manifolds to modify and prep is a C8XX to a D5XX. They have all the extra gusseting and reinforcing material, but none of the bungs, taps and bulges found of D8XX and later. Your C5XX casting would be a second choice- and a good one.
If your manifold is crack free and all the cast holes are intact it will it will be a good, direct fit onto any 250.
Adios, David
