You did not read what I said at all.
Installing a tone ring on a 3.7l requires that you remove the oil pan, windage tray, oil pump pickup tube, oil pump, timing cover, timing chains, rod caps, bedplate, and crankshaft...meaning you'll need a complete lower seal set anyways.
If you're going through the work to do that, being that his moter has a lower end knock, he may as well just replace the bad parts in his motor and call it good. That will save him somewhere around the extra $1500 you want him to spend on a new (wrong) motor, EGR blockoff plate, and tone ring set.
There is literally as much work involved in doing what you suggest as there is in simply rebuilding his motor. And IDK about you, but when I'm taking a crank out of a motor, I'm taking the whole thing apart completely so I can actually get it cleaned out and know what I'm looking at. It's a set of head bolts away from having it completely resealed at that point.