build date confusion

So i was pondering today. I am still in the process of swapping a motor/trany/tcase from another jeep into my 73. I know that the tranny is a T176 with the 300. so when going for parts i use 1982 cj5 4.2l so the napa nerds can get me seals. but the part that always confused me was the motor age. I know it is swapped from a later model jeep. the build code is 212C22. at first i interpreted this a 1978 2 barrel 258 December 22. I always thought about how that motor got mated to that tranny because a 78 was never offered with a t176 so somebody must have swapped it around before i got it. But the thought has stuck with me. today i remembered that in 1980 amc switched to the first digit of the build code as the last digit of the year. so according to the code it could be a 1982 or a 1978 2 barrel 258. meaning either i am playing with a complete power-train from one vehicle or a swapped motor with a swapped tranny later on. long story short. how do i tell if it is a 82 or a 78. I can't go by the carb because it has a Weber on it. my only clue that leads me to a 78 is i bought a valve cover gasket for a 78 and it appears to match and 4wd shows a gasket that looks different.

any big tell offs between a 78 and a 82?

 

carb
distributor
intake manifold
valve cover- plastic or metal
accessories
serpentine belt-
exhaust manifold- integral with intake or stand alone
lots of ways

 

can't tell by the carb its an after market Weber. what about the other stuff is different? I am going to go with 78 though because it is a metal valve cover, V-belt not serp. the intake and the exhaust appear to me to be separate but come together underneath the carb


Also for anybody curious: great lakes clocking ring up to the third setting with a t176 clears the tub and stock skid plate and makes it really easy to twin stick. looks like it shoulda been that way from the factory.

 

Every source I've seen confirms your 1978 build date. I have never seen or heard of a switch to build year in 1980, can you confirm where you heard this? The FSM is the definitive source and it says otherwise. Looks to me like someone either put a 1978 manufacture (1979 model year) engine in a later model Jeep with a T176 or else they put a T176 in a 1979 model Jeep.

By the way: Serpentine belt was only for California models. The other 49 states stayed V-belt.

 

everything i've read says that in 80 the first digit of the build code switched to being the last digit of the year as opposed to the system for the earlier years
http://www.planethoustonamx.com/main/amc_valve_cover_id.htm
http://street2mud.com/webfiles/AMC Engine codes.pdf (page 4)