Hi,
No mistakes. It was very common in the 60s for these "imports" to be registered one, two or even three years after they were originally built. My car was built & shipped from England in 1962, but wasn't registered until 1964. So, the title says it's a '64.
Regarding swapped parts, that does happen. But engine numbers, body numbers, gearboxes, diffs or any other parts with a sequential serial number are also not matched on TRs. Various sub-assemblies were built in different factories, then those parts came together and were stockpiled, eventually pulled from the shelf during final assembly. Numbers are relatively close, but not exact matches.
While your VIN plate should have a little more info on it than my earlier TR4's, more detailed build and shipping records were kept. A certificate listing the configuration of the car when it came out of the factory can be purchased from BMIHT at
https://www.heritage-motor-centre.co.uk/archive/certificate/default.htm
In some states, the DMV might accept the certificate to re-register the car for the actual year of manufacture, if you wish.
Alan Myers
San Jose, Calif.
'62 TR4 CT17602L