WB,
I'm doing a 20g about the same vintage as yours. If you need someone to do the work locally, Bob Day did some choke work for Jim Legg and he was pleased with the work. His shop is in Pico Rivera.

http://www.americhoke.com/

Also, Possibly Les Pittman in La Habra may do choke work. He bent a stock for my last year and I was pleased with the work.