Flywheels
A way to avoid all the dismantling and balancing of all the rotating parts could be to find out what imbalance it was with the 3L flywheel and then to balance the 2.5 fl.w. to same imbalance. Then theoretically one would restore the same balance as the factory engine. Not ideal solution but could work in my opinion...
In reality the late 2.5 & 3 liter flywheels are the same. The balance drill holes were to balance the flywheel only to the correct counterweight offset & position before installation. Same for front pulley.
Engine ballancing , other than matching Piston, Rods, and Rod Big end weights is really a process of guessing what counterweights (bob weights) to use, as regardless, the engine is only truly balanced at one RPM in the spread.
It`s over rated unless you are balancing for 7000 RPM and the balancer probably does not have a clue to accurately calculating bob weights to do so.
If you are going to lighten a flywheel, have the shop measure amt. and location of counterbalance built in at the factory, and after cutting, return the amount of out of balance to the same position & amount.
I remind you that a lot of bull**** has become "holy grail" to Alfa Owners by comments made by the truly uninformed.