There was a user named nochance selling mandrel bends in the for sale forum a few years back who seemed to have good prices and satisfied customers (never dealt with him myself). Also, I've bought from www.metflo.com; they have a great selection of bend radii, materials, and sizes from <3 to 14" dia, pricing wasn't bad.
They were both members here and other Buick boards.
John Kerr's board name was Kerrdogg and I don't remember what Darrin's name was. They both had Buick's, Syclone's and turbo Mustang's. I think John and Darrin both have turbo fox bodies now, Darrin is running Chevy power in his. If I'm not mistaken both are getting tunning help from another old board member Mike Pitts.