70 Exhaust Manifold for 350

[71SRV5VR]

I have a question regarding exhaust manifolds. I have a very original 1971 Chevy C-10 truck, short bed, 350 5.7 lit. 4 bbl. According to date codes, the engine was built in early Spring of 1970. The right manifold number/marking is: 3905364 RH-11 GM...the left is: 3989055 LH-21GM.

Anyway, it appears that the RH manifold was once A.I.R. equipped as it's obvious that that someone removed the device (as was common for more horsepower). I would like to replace my original RH manifold with a vintage non-A.I.R. manifold corresponding to the specs of the engine.

Does anyone by chance know the number of this part? Also, would you happen to know of a person who specializes in vintage exhaust manifolds for Chevy's of that era?

Any help/advice would be greatly appreciated!