Joined: Oct 2018
Posts: 2,182
Likes: 1,055
From: Columbus, OH
Bikes: Pake C'Mute Touring/Commuter Build, 1989 Kona Cinder Cone, 1995 Trek 5200, 1973 Raleigh Super Course FG, 1969 Raleigh Superbe, 1986 Miyata Nine : 1960/61 Montgomery Ward Hawthorne "thrift" 3 speed, by Hercules (sold), 1966 Schwinn Deluxe Racer (sold)
I guess it's not clear what your objective is. Are you looking for a 44-48 t and 34-38 t double versus a 52-38? Do you need to drop the granny gear for weight?
Swapping cranksets from double to triple shouldn't affect your chainline much, but I'd imagine that an indexed shifter would be tricky to set up that way. Piece of cake with friction though.