Advice on my "stock" 340 build

First off, good luck with your build. Sounds like a fun build and you are in the process of a well thought out one. I would go with a 71 stock cast iron intake manifold and a thermoquad carburetor. Aftermarket aluminum heads my be a cheaper way to go especially if you can pick up a used set of heads at a good price. I would also consider porting the heads and intake manifold and also the exhaust manifolds if you do not go with headers by a good porter like Charles Servedio.