I have two 4782 carbs here and both have 4782 stamped in the metering block (below 6525). I think your center carb is built from parts of lesser carbs. The throttle lever definitely seems similar to the 4782 rather than an OE center carb, but the float bowl is a repurposed 1850 part (hence the pipe plug where the transfer tube would go--the 4782 bowl does not feed that spot) and the metering block is OE 340 Six Pack auto as mentioned in the chart. I wonder if someone was trying to tame the more-440-oriented center carb for street use on an LA. As far as the plugged 1850 bowl goes, well, clearly a previous owner had problems with inlet fittings... :D
I agree with @jbc426 that these are spectacular carbs. Much more tunable than the OE stuff. I daily-drove a set on a 440 back in the mid-'90s. I later regretted selling them and it took me more than a year to find another set. If I hadn't, I'd be all over these.
