Because of another link, I stumbled across Mario Righini's web site in Italy, where he offers several 2500 engines (possibly one fits your needs). No affiliation, etc.
Righini has a large collection of great cars, including things like the 1940 Siata MM coupe and the first "Ferrari"; the Auto Avio 815. He always has cars and parts for sale. Raoul San Georgi is a big collector of 6c2500s, and did a "recreation" of the 1939 6c2500 LeMans. He has been buying up a lot of 6c2500 stuff in the last 10 years.
Friends:
There is an engine and trans for sale at www.classicdriver.com. Look at alfa romeo cars listings and at 6c you will find Peter Weisner engine info. He wants 13k sterling for a 2300 1937 engine and trans.
Dear Friends:
Would some one know who might be an Italian Alfa Expert living in Texas arround 15 ago? He might have the original engine to my Freccia!
Thanks
Emilio: do you still have that engine or any engine parts for a 6c-2500? I need a front main cap from a junk block. You can call or e-mail: 805-928-7973 or enginetechmachinellc@hotmail.com thanks, Ron Terry