Originally Posted by bigblockford79
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.
dose have a slightly larger angle.