I recently rebuilt my whole front suspension. I wanted the best parts I could find, and did a bunch of research as to what products currently fill that slot, which was not easy with Moog moving so much of their productions overseas or south of the Border, and Spicer becoming part of Affinia Group, who also make Raybestos.
One thing was consistent was that the service grade was considered what you would put on a car just to pass inspection and quickly sell it.
Since you already installed them, and it is a beater, and you can swap them out easy enough, just check them for wear once in a while. I doubt they will fail catastrophically without warning, they will just wear faster, and might have a little slop built into them when new, and perhaps not fit as well.
In case anybody is interested in what Ball Joints I consider the best and am impressed with is XRF, Same price as Moog, made offshore, but the quality is obvious on inspection.
Here's a Comparison Photo of some Tie Rod ends. Mcquay Norris and XRF. Same exact price. The MN stud was very tight and crusty. The threads were sloppy. The XRF moved buttery smooth in comparison, and the threads were protected and smooth.