You are correct, the J-65. Originally started life as the Armstrong-Whitworth Sapphire and was adapted by Wright as the J-65, and Buick was selected as a second source. This link has a story from 1955 about production beginning at Buick, interesting to read the paper. Another story is of the B-47D beginning flight testing, powered by a Wright T-49 (which was a turboprop version of the J-65). And A&P has picnic hams for $0.33 a pound!