ebay (http://cgi.ebay.com/bmw-e21-alpina-b6-2-8-MOTOR_W0QQitemZ8076208729QQihZ019QQcategoryZ61279Q QrdZ1QQcmdZViewItem)

It's in Germany but the bidding is starting at 500 Euros. Probably cost twice as much just to get it state-side, but for those of you who are interested.
http://i10.ebayimg.com/05/i/07/76/b1/ce_1_b.JPG

its difficult to say that it really is an alpina motor though. It could just be a dressed up M30 running triple carbs because they didnt come with the 45 setup. Would have to take the engine number and contact them to find out what vehicle it came from.