Re:
I'll second what Raidan73 says.
Look at 1990's bikes made of 531 or 631 (or their equivalents from Columbus, Tange etc) from people like Raleigh, also Ribble, Cougar / Dolan, Orbit and any number of other half remembered manufacturers.
I built my first ever road bike three years ago and am very glad I did as I really enjoy putting in the miles, increasing my fitness and enjoying some great rides.
When you find something you like the look of, ask in the road section for opinions, some people can be a little forthright and (dare I say it) snobbish, but you'll get some good information.
Watch out for sizes; mtb's and road bikes fit in completely different ways, so probably the first thing to do is figure out what size you need. Trad is to go big frame and no seat post showing, modern is the reverse, and pay attention to reach, as you will spend more time on the brake hoods on a road bike, and that can easily put another 100 to 150mm on the reach.
Have fun searching, there are loads of bikes out there, but like mtb's, they are not all diamonds in the rough.