I've got an old Huffy tandem that I'm planning on doing that with.

On the Huffy, the front pedals have a smaller gear than the one that connects to the rear chain. I'm planning to use that with a long chain direct to the rear wheel, which should make it lower geared than it was orginally. (It's a single speed).

I would never cut up a bike that had any value as an antique or classic; there should be enough old worthless beaters out there to cut up.

On the Huffy frame, the front pedals are very near the front wheel, meaning your toe can clip the front wheel. And the bike is just all around unimpressive, even if it was in better condition. And frame size is smallish. The moral is, you can't start with a $100 tandem and expect to build a $2,000 dollar Big Dummy out of it. You start with a $100 tandem and build a $110 Frankenbike out of it.