I think there's a problem with putting conservatism as the opposite end of socialism. Conservatism, the way I understand it, refers to the idea to keep the social order as it is, or if it changes, it happens gradually. It may be divided into two big groups: social conservatism and economic conservatism. Social conservatism refers to idea of maintaining social norms (which is why it refers to the 'old religions') while economic conservatism refers to libertarian idea of minimum-government (although not as extreme as anarchis which is outright anti-government)--born from European classical liberalism. In the early 19th century, classical liberalism seemed to be the mainstream idea in Europe (at least in UK). That's why Marx and Engel refered it to 'conservative' social order.
That's what I meant about terms like conservative being relative. In the old Soviet Union, the "conservatives" are the die-hard socialists.
While the terms "radical", "liberal", "conservative", and "reactionary" generically refer to people who want a huge change, a significant change, minimal change, or else a change back to the way things were, the terms "liberal" and "conservative" have also come to describe specific target social conditions. The use of the terms for that purpose is in some ways unfortunate, since it tends to muddle their meanings, but I don't really know any non-pejorative alternatives.