FWIW. Consider which components you wan use
Buy them (of course, for a ROAD bike, I recommend Campagnolo shifters), and install them on your current bike frame (if you are methodical about replacing one component at a time vs. stripping your current frame then you will see how easy-or-difficult the future task will be for you) to get a sense of what is involved ...
Don't bother buying either the seatpost or headset since the future frame may not use the same sizes ...
Worry about the frame, last ...
Being old school, I would try to buy a frame with an ENGLISH THREADED BB shell ... that may be hard to find unless you are going to buy a "custom" steel frame OR some/(all?) Titanium frame ...
AND, a head tube which uses a traditional 1 1/8" headset.
