Convert to and from?
 

Hi I have a 1980 Miele which i use as my commuter. I was thinking of making a SS/FG with a flip flop hub out of it. But i might want to switch it back some day to a geared bike. If i keep the cassette, derailleurs, extra chain ring and the original wheel (and make up a different wheel with the flip flop hub).
It would be fairly easy to switch back and forth right?

I plan to keep both brakes on it.

.. i suppose i would need to keep the old chain too.

I ordered a Cross-Check complete and a fixed drivetrain to do just this. I got a wheel, a chainring, a cog and a chain. I've never ridden fixed, so I wanted to make sure I had something to ride in case I hate it. I imagine that I might need another crank as the bike comes with 175mm ones in my size.