just checked my 351 2v C and the carb port is capped and the manifold red box is plugged as well.

 

It looks like the red is the temp sensor...the others I can't make out.

 

Temperature sender on a Cleveland is on the front of the block, below the thermostat housing. Remember there is no water in a Cleveland intake manifold.

 

The "red box" looks to me like a manifold vacuum fitting that is plugged off. The "yellow box" looks to me like one of the screws that holds the choke housing to the carb, but looking again, guess you mean the vacuum fitting/line. I believe that is ported vacuum to the distributor but may go through a TVS before it gets there in the correct configuration. The carb vacuum port should certainly appear on the vacuum diagram. The other port should appear as manifold vacuum.

 

I think the top yellow box is one of the main vac lines coming off the carb block.