Originally Posted by DeRanged mudder
On a carburated engine it is a huge waste of time to test fuel pressure. If the fuel pump is pumping a good amount of fuel out, you have enough pressure. Much easier to do a flow test and you can do a visual test of the quality of the fuel at the same time.
15 lbs of vacuum is defiantly a problem!!!!!! 15 inches of vacuum could be a vacuum leak which, would give you the same symptoms as lack of fuel. Check the base gasket.
I only pull about 13-15" of vacuum @ 850 rpm on my 5.0 HO. If the engine in question has a different cam than factory it may produce lower vacuum without a leak.
Did anything change with the carb/engine during the swap besides the sheet metal that surrounds it? How long did it set before the swap was completed? If it sat for a while it may have gummed one of the primary jets or need valves a little. Float height might also be an area of concern, even if it ran good in the other vehicle, its new home may have a different slope to the intake and might make the previous float level too low.