Decoding fender tag

I recently bought a 71 Duster and im trying to figure out a few codes on my fender tag and was wondering if somebody could help?. What numbers i cant find are...GT2 which appears twice and TX9...921...VL29...C1E and then the #s...136042 and 108604. If anyone knows what these mean please let me know . One more thing i dont understand is the code U which says Built to specifications for USA order. Does this mean my car was built in Canada? or the USA? THANKS
GT2 is likely a paint code, body and roof.

921 scheduled production date

TX9 maybe upper door frame.

VL29 is a duster body style

C1E is engine code, model year, factory (los angeles)

136042 order number
108604 build sequence number