The last 6M's were Shooting Star engraved...so I think the OP is speaking of a late 60's-early '70's 6M.
Quick answer to your question: NO, a late-model 6M neck does NOT fit a Chu. Even if it did, how do you get around the double-socket ? You'd have to either alter the neck of the 6M or the receiver/ferrule of the Chu.
Generally....Conn alto necks were pretty consistent over the 60+ or so years that real Conns existed.
A Wonder or New Wonder (Chu) neck fits a 14M (Mexico or usa) or 50M or 7M of Pan American...and vice-versa. A '37 6M neck fits a '69 6M like a glove....and vice-versa.
So...if what you need is a neck for a Chu, look for a 14M or 50M Director... or Pan American.... horn or neck.
The problem with a 6M is (of course)...the double-socket. None of the above fit a 6M double-socket receiver/ferrule...it was a different diameter. Even if it did...you'd have to get a tech to rig up something to make the 6M receiver tighten the ferrule....which becomes a hecka complicated proposition !!!
This, as Saxismyaxe points out...is only ONE of the many issues of switcheroo necks. The tenon fit is really almost the least of your worries...because now you have to concern yourself with intonation and tone.
There's the tenon diameter...there's the overall length of the neck...and there's the taper and bore of the neck from mouthpiece to tenon. Relatively significant differences in the latter two can really mess up the horn's sound and intonation. In the tech section it has been suggested that octave pip location comes in a distant fourth to these first three issues.
(This is what burns me up about sellers who claim "slap our new neck on your horn and watch your problems disappear !" Yeah, right. :tsk: It's not as easy as that, even if the tenon fits perfectly).
That said...the 14M, 50M, 7M, and Pan Am necks are all pretty much interchangable...maybe requiring a slight tweak by a tech (i.e. slight tenon expansion or compression)...but their lengths and bores are pretty consistent with one another (although you may have to mess with the octave key rings to get them to meet the octave stem of whichever horn you are putting it on).
Just at a quick glance, the Chu neck (while fitting a lot of other Conn receiver ferrules) is the exact same length as a 14M neck and the pips are located within about 3mm of each other...BUT the opening diameter on the m'piece end of a Chu is significantly NARROWER than on a Director 14M. Which means the Chu's neck tapers much more dramatically to its tenon than does a 14M's neck.
Would this throw something out of whack ? Probably. But could it possibly work OK ? Yes...possibly it could.
IF it messes with tone or intonation....would it be correctable ? Maybe, given an experienced tech.
I am assuming from your Q you have a neckless Chu. In that case...take my advice above and try to find one of the horns or necks I mentioned ~ I say 'horns' because a fair amount of the time you can find a whole beater Director or Pan Am for under $100 (add to that maybe $25 of tech work for a perfect fit)...while finding an actual Chu neck or having one made or significantly altered can cost between $250-600.
Your only other option...which will end up costing about the same...is to just try to nab three different individual sax necks (maybe get the specs of an actual Chu neck...THEN ask the seller for 1) the tenon diameter...and if it is w/i around .5mm of the actual diameter needed for a Chu...it's a good candidate. 2) then the length of the neck...if it's shorter by less than about 3MM...or if it is LONGER by whatever...it may also be a good candidate). Slap 'em all on, see which one sounds and intones the best....and there you have it.
Since single, unidentified necks on eFlay tend to go between $30-50...this will also cost you around $125-175, in the end. So it's a bit of a wash between this and just grabbing an old Conn second-line horn.....and I'd be happy to buy the body of the horn you find for $40, so you can even recoup some $ there....