Sounds like the guy is either a complete idiot, or his wife told him to get rid of the money pit....seller: OK honey, I will put it on Craigslist......stupid *****, it will never sell for 25K.....look honey, it will not sell, can we keep it.
The theory of operation is the same, the tuning procedures are the same, but the actual parts used will be different. I would suggest you get the book "How to Build & Power Tune Weber & Dellorto DCOE & DHLA Carburettors"
I would not use that specific pump, the LOW side of the pressure range is on the HIGH side of what our carbs need. Mr Gasket may make one with the right specs though? The Facet I mentioned is quiet and reliable. Had mine mounted at the back of the car for 4yrs now... three of that was driving around Vegas in 120deg heat, after the Holley fried from the heat.
One of the byproducts of all Hydro-Carbon combustion is...drum roll please...WATER. Until your exhaust gets hot, that water will transform from a gas (steam) to a liquid (water and water vapor). This liquid water will pick up all the carbon soot in your exhaust..esp carbed engines...and throw it out the back. What it does tell us, is that you have incomplete combustion during some part of your cycle...could be overly rich or not....my Dyno AFR's look pretty good..for making power, but I have a sooty tailpipe FWIW