Some of those old steel road bikes were spaced 120mm, most were 126mm. Staying as a roadbike involves stuffing a 130mm hub into a space which wasn't designed to take it. I know you can spring it, or even get it cold set, but if I found a road frame with 120mm spacing and long slot dropouts, my first thought wouldn't be maintaining its spiritual purity by squeezing a cassette full of sprockets in there :-)
Some of those old steel road bikes were spaced 120mm, most were 126mm. Staying as a roadbike involves stuffing a 130mm hub into a space which wasn't designed to take it. I know you can spring it, or even get it cold set, but if I found a road frame with 120mm spacing and long slot dropouts, my first thought wouldn't be maintaining its spiritual purity by squeezing a cassette full of sprockets in there :-)