[DougD]

No small blocks, either in a Shelby Mustang or a Cobra, came from the factory (Shelby American) with dual quads. 1967 GT500's (428's) had dual quads, and a fair number of big block Cobras (427's & 428's) came with dual quads, but that's about it.

Woodz428 is correct - what you have is an aftermarket part distributed by Shelby through one of several parts catalogs issued late 60's-early 70's. If it's mint, I'd guess it'd be worth somewhere between $500-$1000, depending on who you talk to.

Sounds like just the ticket to make that small block scream.