You may be interested in SCM’s Planning Your CM Education. It’s a great resource for designing your own curriculum. That may be your best bet.
For 3Rs, most math is secular…either RS or MUS are good options. We are currently using ELTL for language arts, which would work fine for you. There is an occasional Bible verse in the copywork, but I think she provides an alternative passage as well…I haven’t played close attention to the passages, since we are using SCM’s Print to Cursive Proverbs in its place. I believe Spelling Wisdom would be fine as well…it mostly includes famous quotes and book excerpts.
We are currently using SOTW 2 alongside SCM’s Middle Ages. I know it’s used by both Christian and secular homeschoolers. You may find it a good choice for history. I’m sure there are tons of good science options, but I’m mostly familiar with the Christian options.
Another resource I’ve found helpful is Cathy Duffy’s reviews. On her website she lists whether a curriculum is religious, secular, or usable by either type of homeschooler. I find this very helpful when selecting curriculum for the coming year.
In place of hymns, you may want to study folksongs…we follow the AO selections. Instead of scripture memory, maybe add in some poetry memory work. CM methods could easily work in a secular setting.