I would suggest just replacing the fuel line its cheap, fuel sitting in lines a long time can case built up that will flake off when running and make a carb you just cleaned dirty
so for the small price and amount of line, just replace it and save yourself some headaches!
as for tubes, if tires are dry rotting, they won't be much help for long
look on local craigslist or local dealers for take off tires, many times they can be pretty darn cheap
and even used one's too!
as for changing gearing again, if your going to do so, when you change a sprocket your supposed to change BOTH sprockets as chain at same time, due to the fact the things wear into each other to seat, when you change just one sprocket or just a new chain, you will have excessive wear and tear on ALL things, getting you must shorter life of all 3 things!