The later 2 c have different yokes as they have Guzzi type forks instead of marzochi. i believe the guzzi v50 has the same forks as a 250 2c they also have 2 caliper mounts. The later 2 c has an alloy barrel and larger carburrettors is said to be 32 bhp instead of 26 bhp on the earlier model.
The bike itself is only 231cc there was a kit to bore the iron barrell out to 250cc but i am not sure what pistons they used. The Benelli motobi club know some people who have tuned and raced some 2 c.
I loved both the 2 c i had in the past great 2 strokes !