Nice bike! congratulations!
Looks to be an Early aluminum Alan with clamped on cable guides and DT shifters....I dunno, maybe very late 70's or very early 80's?
IIRC, I think they were all italian threaded, so it will be a bit harder to find components from it compared to English threaded bikes like later Vitus models. The thing I like about Alan is they went to the trouble of actually having a head tube like traditional steel frames. Vitus did it sith just a one peice cast aluminum had tube/top and bottom lug which does not look as elegant, plus Alans have that bif of nice looking scroll work on the from tof the fork crown lug. The stops and guides on later Alans seem to tend to be susceptible to metal fatigue damage and crushing if not handled or adjusted carefully as many for sale at ebay have them either missing or damaged.....but I guess you will not have that prblem with this Alan!

Chombi