No, it isn't worth doing a reverse conversion on. The cost of the parts add up to more than the game is worth, and by doing a reverse conversion you are just killing another one somewhere else, and the OTHER one might not have ever been painted over.
In general its not worth doing a reverse conversion unless you already have a lot of the parts. Otherwise it will almost always add up to higher than the cost of a complete unit, and you aren't "saving" anything, you are just buying parts that were either just ripped out of a dedicated unit last week, or parts that could be used to repair an almost complete unit.