355 Engine Serial No vs Year built / Spec

Hi all,
I was wondering what engine spec and especially what valve guides I have.

I did only find limited info on engine serial numbers in the web.

My car is 1996 GTB with original engine SN 42'6xx, but now a F129C with SN 51'2xx is built in. No records of previous owner as when or why this was exchanged.

Is it safe to say that that engine is a spare stock engine with newest spec? What engine SN had the last delivered F355?

Many thanks for all inputs.

 

Hi all,..
just found another thread stating the production month is casted into the crankcase, but probably also on the cylinder head.
https://www.ferrarichat.com/forum/threads/numbers-matching-vin-assy-engine.473981/

I will try to read the production month of the cylinder heads and crankcase with a boroscope and this should bring me a step further.

Regards