Let me try this again. Some of these questions you could have answered if you looked at those pictures I suggested.
Sounds like the intake and maybe the carb would have dates prior to the engine assembly? Is the carb added during assembly 100% of the time? All other components including fan blade, dist, fan belt, fuel pump, coil, ex manifolds, starter would have been installed at SJ? I'll take a look at the assembly line section for additional photos of what was included in the engine assembly.
Yes as we understand it and examples have supported the intake, distributor, bellhousing if its a manual transmission car, carburetor, exhaust manifolds, fuel pump, coil and bracket, valve covers, water pump, thermostat housing, timing cover, harmonic balancer, and I'm likely missing something else would all be dated before the assembly date unless you believe for some reason that Cleveland took a half build engine and put away someplace and finished it later leaving a hole in the production line. IMHO its a big stretch.
Items like starter, fan, pulleys, belts radiator hoses, heater hose, throttle linkage, transmission and alternator were added at San Jose in the case of your car.
If SJ added the remaining engine parts, I have to wonder and visualize how the Nov '65 dist and Feb '66 ex manifolds ended up on the engine not too long after it was assembled. Then delayed installation.
Think you have that backwards given what you provided in your first post
"Deck stamp date of block Feb, 9 '66. ................. pass ex manifold is dated Feb 1, '66"
According to this the manifold was cast 8 days prior to the engine being assembled. Tight but not cast after.
Would I want to use dated fan blade, fan belt, coil, alternator etc. fairly close to the dist and manifolds to go along with what I'm quite certain is original to the car or dated closer to the projected build date?
The coil is easy since you just stamp the date of choice. The alternator is not stamped in the metal and again you can just pick out a date and ink stamp it For fan belt its a bit more difficult. Have not seen anyone reproducing original type fan belts. There are ones Kevin Marti is making but not certain if they are made with a date for the early cars.
As far as choosing parts dates and using the widest spanned of dates you have (between Nov 65 and Feb 66) is your choice. Dist should have a date prior to the engine assembly date. Just for reflection I looked through what records I've collected and I found the following
-Nov 65 assembled engine Nov dated distributor
-Dec 65 cast engine with a Nov dated distributor
-Nov 65 cast Dec assembled engine with a Nov dated distributor
-Dec 65 cast Jan 66 assembled engine Nov dated distributor
More from other parts of the year
-Nov 65 assembled engine Oct dated distributor
-April 66 cast May assembled engine April dated distributor
We could expand out to look at 65 or 67 also but that is a quick look at some examples.
As for being confident about it all being original that is your choice. Don't let the answer you want tell the story. I've experienced too many stories told by original owner that we provided were not correct. Don't think they were always making up stories just poor memories or in at least a couple it was possible they never knew and the issues were done maybe before they took delivery or during servicing at the dealership.