Another recycled post - Someone at npmusers was looking for English language adaptations of the Graduale Romanum...

There's an "American Gradual" of sorts, available from St. James Press. I believe it's based on the 1979 Episcopal Book of Common Prayer and the NRSV. The review I saw last year found it a bit prosaic (or maybe the word was "artless"?), but if you're going to paraphrase anyhow, this would be a good jumping off point. And I think the gripes had more to do with pointing the chant than with the text itself.

Episcopal/Anglican resources are generally pretty good for this kind of thing - theologically and liturgically very close to RCs, but they switched to English 400 years before we did. So the old prayerbooks (1928) and hymnals (1940) are good sources too, though you'd likely want to fix the Aulde Englifh...

Dr. Paul Ford's "By Flowing Waters", available from Liturgical Press, puts the Graduale Simplex into English. It is also based on the NRSV, but shares none of the criticisms accorded the American Gradual. It is an excellent work. BFW is also about 1/5 the price of the AG. I'd start there.