A couple of links to fuel injection systems for the in line 6:
http://67-72chevytrucks.com/vboard/showthread.php?t=370527&highlight=LineGeneral discussion on fuel injection systems for the in line 6.
http://67-72chevytrucks.com/vboard/showthread.php?t=313766&highlight=inlineSee the posts by 'TP from Cntl PA', he installed a GM TBI from Howell.
http://67-72chevytrucks.com/vboard/showthread.php?t=276823See the posts by 'greg64', he installed a 6 injector TPI system, them removed it for a TBI system due to fuel distribution issues with the siamese intake ports. Another thread with a good collection of photos of modified in line 6's.
http://67-72chevytrucks.com/vboard/showthread.php?t=276823&page=16See the posts by 'K5 Addiction', he installed a F.A.S.T. fuel injection system.