My memory of the 70s and 80s is that Republican Party was not particularly anti-evolution at the time. There were discussions and debates about "Evolution and the Bible" and such, but they didn't have a particularly partisan character yet.
What I recall being much more significant were environmental issues. Although the Clean Water Act and Endangered Species Act were passed under Nixon, by the time the Reagan administration rolled into town the Republicans were pretty strongly on the side of pollution and extinction. Many of you are probably too young to remember Reagan's Secretary of the Interior, James Watt, but that Wikipedia article covers the high points. Basically, he was completely on the side of extractive industries (including forestry and mega-agriculture). He justified it with Christianism: God wants man to have "dominion" over the earth, and besides, Jesus was coming back any day now.