The addition of the songs "in the back" (151 and following) are selections from what we used to have as a psalter. The mixed edition you mention in the OP is only a few years old. While many are not as literal as the first 150, few are Christianized or are particularly modernized, to my recollection. (Disclaimer: haven't sung them all, but they picked perennial favorites for inclusion). 173 is only the first eight verses of Psalm 62, for example, but with faithful wording.On the other hand, 180 (Psalm 72) is entitled "Christ Shall Have Dominion." My favorites from Bible Songs are mostly in the 190's.
If you have a hard copy of the edition, there's an explanation of psalm-singing in the ARP included in the front.