Bacciagalupe

If by "Sea to Sea" you mean a 10+ week trans-America tour, I'd probably want to swap out, uh... everything?

Seriously, for a tour of that length a road bike with a standard double is just not going to work, and the expenditure of the changes is anywhere from 1/3 to 1/2 the cost of a new touring bike. You would want:

- low gearing, preferably a triple that extends down to the low 20's in terms of gear inches
- wide tires
- fenders
- an upright riding position
- long wheelbase (for better handling while loaded)
- cantilever brakes (optional, but provides for more stopping power than calipers and wider tire clearance)
- bar-end shifters (also optional, but handier in many ways for touring)

Swapping out the gearing and tires alone will run you more than $300. And are you going to swap all the old parts back on when you're done?

So if you're talking about a long tour, I'd seriously consider getting a Surly Long Haul Trucker "complete," Jamis Aurora or Novara Randonee....