1964 Giulia Spider 101.23
I have a similar problem.
My car is a 1964 Giulia Spider, chassis number AR 379654 and engine number AR 00112 – 15119. Coudn't get the confirmation of the engine number from the ARCHIVIO STORICO ALFA ROMEO, only that the series is correct.
Based on the Fusi list the engine number would probably not be correct but then the list is a bit «funny».
Attached is a summary of the Fusi information for Giulia Spiders and you will see that a total of 9.953 cars were produced corresponding to a total of 11.116 engines.
But more than that, year by year the numbers clearly don't make any sense, mainly for 1964.
So, althougu it does not agree with the numbers on the Fusi list ,I am quite sure my engine is the original.
Hope this helps