I don't think your relative strengths in different types of terrain have much to do with your actual body proportions. There are a whole lot of spindly, long-legged guys who are great in the mountains, and a whole lot of others who are best in the flats.

There is something of a correlation between proportions of muscle-fibre types and body shape. Athletes with high proportions of fast-twitch fibres, who are thus more adapted to producing bursts of anaerobic energy, tend to have bulkier muscles. Sprinters like Cipollini and Zabel, with their huge thighs, are typical. Then you get the class time-trialers, like Christophe Moreau and David Millar, who have proportionally more slow-twitch fibre and are better adapted to steadily producing power just below their ATs for very long periods of time. These guys are best suited to endurance races and stages.

There's really no way to say which muscle-fibre type is best suited ti climbing, since there are a whole lot of different kinds of climbs. I suspect l"angliru favours climbers with a high proportion of fast-twitch fibre, while something like Ventoux, with is long, steady grind, favours the slow-twitchers. One thing most of the Angels of the Mountains have in common, though, is that they carry very little extra weight in body fat [which is a disadvantage on a long, flat stage]. They tend to have very slight builds like Roberto Heras and Roberto Laiseka.

But leg length doesn't really come into it... After all, didn't Luc leblanc have two legs of different lengths?