What would you think is the most correct date code for a carb for a 1971 Duster 340 with a SPD of July 9th, and the engine was forged on January 19th 1971. (matching #s car)
#1 March 24th 1971
#2 July 1970
#3 June 30th 1971

#1 would be my choice

#2 is too far away. Especially on a higher side production motor like a 340.

#3 is too soon.

My '66 Hemi is SPD April 27, 1966 and has March 1966 carbs. Much lower volume production motor.

I believe you can see the assembly date on your 340 by looking at the block stampings just under the head gasket on front of drivers side.

Thank you for your response. I will look for that assembly date on the block under the head !

Is your hemi a known original car? I would have thought C6 (mid march carbs) would have been too late for an Apr Hemi, unless actual built later. Seems like hemi had earlier lead on carbs. Corrected date

It may have been a typo in your post, but his carb are dated C6 / march 1966 not C5 / march 1965. I would say with a late April SPD that most likely about right. I have a complete 3/66 casting hemi that has C6 carbs and fuel pump. Also as you mention it may have been it was built a little later than the SPD as well.
Matt

your engine block is CAST
your heads are CAST
your intake manifold is CAST
a 1971 340's crankshaft is FORGED

CAST parts have dates on them indicating when they are CAST (not machined, not assembled)
your engine assembly will have an assembly date STAMPED on it below the driver side head. also, is your car's engine stamped GW340 (orange engine) or GM340 (corporate blue engine)?

It is corporate blue

Yes error I corrected date. What was assembly date of your motor Matt? Hemi carbs made in batches on certain months only. C6 was they last batch for 66 cars until. Do your carbs have tags? Any ink stamps?

The C6 carbs are on my 66 Satellite. I have got to that step of documenting the motor details yet. Car has been in somewhat continuous operation since 1966. My cars Scheduled Production Date SPD is Apr 27, 1966. But I don't know the actual production date.

engine assembly information

Perfect !

Thank you.

This may sound like a broken record but the fact remains, there is no "normal" when it comes to date spreads on carburetors. As long as the list# is correct for the application and the date code is prior to the engine assembly date it's fine (grey area exception being a date too close, as you need to add a reasonable amount of time to allow movement from the carb manufacturer to the engine line). I've verified original engines with carburetors manufactured 4-8 months prior to the engine assembly date, and only a couple weeks prior. There was no inventory "first in first out" back then. Also, in dual or multi carb applications, it was common for the individual carbs to have date codes that are weeks or months a part, some matched, some didn't, it was random .02

I wonder about supply chain timing. Since I track Hemi carbs, and the tag has a day not just month makes you wonder. When a batch of hemi carbs lets say 13Jun68 were finished (all Jun68 hemi carbs tags would have that date code). Is that the day they were shipped, or was it an inventory count day at Carter? Followed by packing, shipping, receiving at Chrysler, inventoried and moved to the production point. Did the engine factory get them directly? So how long did all that take before it was ready to put on a motor.