This is a great tool from the Heritage Foundation. You can sort and filter the information several different ways. Here is the link: http://heritageactionscorecard.com//members.
One interesting observation is that there is very little overlap. There are only a handful of Republicans that are more liberal than the most conservative Democrat. The most liberal Republican is Representative Chris Gibbons of New York with a score of 23. The most conservative Democrat is Rep. Jim Cooper with a score of 33.
Among Republican Senators Lamar Alexander scores a 47, the same score awarded Mississippi Senator Thad Cochran, making him more liberal than John McCain or Senator Bob Corker each with a score of 53. Of the 41 Republican Senators only 3 are rated as more liberal than Alexander.
I find it interesting that Senator Lindsey Graham, who conservatives love to hate, has a respectable score of 59.
Only three Senators scored a perfect 100 and they are Rand Paul, Ted Cruz, and Mike Lee.
It is worth keeping in mind that this scoring is based on only 19 votes. Someone else may have chosen different issues and the scores may have been different. Also, if I was doing the scoring I would give more weight to some issues than to others. If you go to the site you can see the issues included in the scoring matrix and see how any representative or senator voted on that particular issue.