If parts and components are available, engine assembly can be done anywhere using appropriate wrenches and with skilled workers.
Whereas, engine parts and components manufacturing such as cylinder head, block, crankshaft etc, need large mills for casting and mother machines (milling, lathe, shaping, boring, etc).
2-3 years production is too short to have a return of investment for the design, cnc programing and cost of plant and machineries to manufacture parts and components.
There could be parts and components inventories somewhere else ready to be churned by newly built assembly plant. If it is previously produced, there is already an established assembling standards so it will be also a good OJT opportunity for new workers trying to develop skill.
High power version of R428 (the RA428) came in 2007.
If there is a major issue such as crack cylinder head like this
Wrangler 4dr 2.8 CRD Engine woes - 4x4 Community Forum
Production can be prematurely put on hold causing lots of parts and component inventories.
In the above link, cylinder head failure occured after clocking over 100,000km. Fatigue could be the cause but its already out of warranty mileage.
A428 came in 2010 to improve the R428.
Chevy/Numbah calls the RA428 Duramax1
while the A428 as Duramax2.
In the internet you can find remarkable features of Duramax 2 as follows:
What I see in the above features are countermeasures for cylinder head crack caused by fatigue.
Cyclic external loads like: metal expansion due to heat, restrained contraction as metal cools, moment load by cantilevers (extremities such as manifolds) and vibration could cause fatigue.
How effective is the countermeasures is.... only time could tell.
Sorry for spoiling the fun and excitement. Just wish my analysis is wrong....
Too much said and done from me.
For duramax 1 owners, just be cautious. Check your coolant level before long drives. Look for unusual bubbles immediately after a cold start.
Peace to everyone.