Hey - Bike looks in great shape - May need new wheels, tires, tubes - Harris has a pretty good set at about $120.00 - Older wheels can't handle more than about 194# and looks like your spoke nipples are about to pull through - Gear set threaded? - 120mm or 130mm? - New wheels and a tune up are the only things this bike may need - NICE...

But to go to a Fixie (fixed gear) lining up that front crank can be a real chore - Maybe stick with your larger ring in front and space it inward then take your freewheel and respace your third or fourth gear out and fix it there - Just remember with new wheels this is a pretty good bike just the way it is - My only experience on fixed gear bikes was a few times as an athlete on a track - Be sure to read Sheldon Browns articles and links on fixed gear bikes... Good Luck