In the KJV of this passage, we read Whom God hath set forth to be a propitiation through faith in his blood.
Most modern translations do not have this reading, they leave off in his blood away from faith even though in the original Greek word order, KJV is the most accurate.
For example in the ESV, we get this whom God put forward as a propitiation by his blood, to be received by faith.
Notice, how the ESV moved his blood closer to propitiation, technically differing from the KJV. What is the reason for this? Well, the ESV translators following others do not want the readers to put their faith in the material blood of Jesus, that red liquid part of the human body.
IMHO, the KJV is quite accurate here which brings me why I posted the picture of the late Aussie NT Scholar Dr. Leon Morris. Many years ago, I went to converse with Dr. Morris in his Donvale home, a suburb of Melbourne. I got to discuss this thing about the "blood" of Jesus with him when he agreed to be interviewed. He said to me, that whenever you read "blood" in the NT, it does not suggest per se the material blood the flows from the body. He said, each time you read it, equate it with "death". The KJV is not suggesting the material blood per se that is the object of faith, but the death of Jesus as faith's object. Hence, properly understood the KJV does a very good service of pointing the reader to the death of Jesus.
In my readings, when people speak of believing in Jesus, faith in Jesus etc., what is exactly neglected is what is it in Jesus one should believe? This is the reason why in my last interaction here, I asked what exactly is the object of faith? In Romans 3:25, the object is the death of Jesus, that his death is payment for our sins. That is the object of faith as taught by Romans 3:25.