Mark,
First of all, since you are looking for a final internal temp of 140, this means you are looking for medium to medium-well doneness with the roast. I hope that is what you are shooting for. And if you are cooking to an internal of 140, then the outside slices will be medium-well to well-done with the slices being a little less done as you get closer to the center slice of the roast but still no less than medium doneness.
Second, taking the roast to 115-118 and then leaving in the 140 oven for another four hours, if that roast is not at 140 when you take it out, it will be darn close.
As I said before, you can always finish a slice a little more once you cut into the roast. But if it is too far done, there is no way to recover that.
Please come back and tell us how it came out.