Upgrading Groupset: Old to New First time here. 
Am thinking of upgrading my '86 Schwinn Peloton's brakes, shifters, and derailleurs with lightly used indexed Tiagras including brifters. I ride the bike so much that I really want to feel safe in traffic and see what lighter, modern components can do for it. I'll keep the original stuff and restore them to the bike if I decide to sell or hang on the wall.

Any problems with my plan that any of you can see out there or is it too much trouble? 
Thanks.
JM
You will need a new rear hub that can fit a modern cassette, and to spread the rear fork for the wider hub to fit.

Also, you need cable stops that fit at the place of down tube shifters. They may be included in the groupset, but if not you need to buy them separately.