Tech Tip #2: how to determine the year of your 1HX engine:
1. Look at the #6 cylinder RH side block boss: You will see a number: this number will reflect the casting and machining date of the block itself. (-YR|MTH|DAY)
2. Examine your main bearing cap assembly at the #1 cylinder, RH side, behind the water pipe and in between the alternator and the main bearing cap: You will see another number: (-YR|MTH|DAY)
These are your casting/machining dates. Remember: there are two major processes in engine block building: Casting/machining and assembly.
In the case of legacy Toyota engines like a 1HZ (34 years of continuous manufacture), they are still, generally, hand assembled; a human is in the loop. Current Toyota engines are very automated in terms of assembly. Less human.
3. On the front of the block, the top freeze plug, you will find notations: it generally corresponds (at least at Toyota Industries Corporation) to the month/day of assembly and the manufacturing assembly line.
In this case, June 11; Engine Assembly Line 2:
That will allow one to order the correct parts for correlative applicability.
HTH