Big-time cocaine and heroin dealers could face fines of up to $8 million under a bill signed into law by Gov. George Deukmejian. AB 2574 by Assemblyman Jack O'Connell (D-Carpinteria), which takes effect Jan. 1, sets the maximum fines for possession of heroin, crack cocaine and powdered cocaine according to the amount of the drug. Top fines would be $100,000 for possessing less than three pounds, $1 million for three to 10 pounds, $4 million for 10 to 25 pounds, and $8 million for more than 25 pounds. Under current law, the maximum fine for possessing heroin is $50,000; it is $20,000 for crack and powdered cocaine. O'Connell and Los Angeles County Dist. Atty. Ira Reiner said when the bill was introduced earlier this year, they patterned it after laws in other states and a federal law signed last year by President Reagan.