The short one is either low performance 409 or 348. The long one is an over-the-counter manifold for special high performance 409 engines. Not sure if it was available on the car during production, maybe just a parts counter item late '62.
My memory is a little fuzzy but here is what I recall. First off I am talking strictly about hi-performance 409s. The manifold on the left was factory equipment up through 1962. Here is the fuzzy part. I believe the 1963 through 1965 manifolds were changed. When I rebuilt my 1962 hi-perf 409 in 1973 I needed new exhaust manifolds so I went to the local Chevy dealer and bought a new set. The new ones looked a lot different. They were more streamlined castings. I still have them on the engine. The thing is this. I am not so sure that mine are as long as your picture on the right which leads me to suspect that you may in fact have a manifold from the 427 Z-11 W engine that came with a valley cover, raised dual quads and cast streamlined headers. A good chevy parts man might be able to confirm that.
Left one is a standard 348 (all) and low-horse 409 manifold. There are varying outlet sizes for this design depending upon which engine it was originally intended. You'd need to cross-reference the cast number to determine original application. Right one is a '61-64 high-horse 409/Z11 manifold, and were also installed from the factory on those cars. Reproductions of these are available, but expensive. Part numbers were #3822295 and #3822296
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