JEGS offers header accessories and exhaust header flanges for many common engines and applications. Quality header flanges are usually 3/8" thick to provide a strong flange to mount your headers. JEGS also has alternator brackets to replace stock brackets when you add headers.
Doug's Headers Motor Mount Adapter Plate Kit 1964-1974 Buick/Chevy/Pontiac LS1 4.8/5.3/6.0L
Doug's Headers Motor Mount Adapter Plate Kit GM LS1/LS6 Into 1973-1987 Chevy C10 Trucks