The '92 FC3 [2nd gen] and '93 FD3 [3rd gen] exhaust manifold bolt patterns look identical.
Are they interchangeable when not used in an automotive application?

Harry

If you are referring to the exhaust bolt patterns on the rotor housings
the answer is yes. The exhaust manifolds however are completely different
of course. The rotor housings are interchangeable however there may be detail
improvements to the 3rd gen rotor housings.

Paul Lamar