Eathann, you're right on about the Kepler GTX 670 card (300 Series, Signature below) - supports Metal v4 on Mojave PB 10:
View attachment 351734
Mojave includes drivers for full acceleration, as you indicated. This EVGA 600 Series card was released in 2012, and according to
http://gpu.userbenchmark.com/Compare/Nvidia-GTX-670-vs-Nvidia-GTX-1050-Ti/2181vs3649 compares reasonably well with the current Nvidia 1050 Ti 4GB graphics card.
Bought this GTX 670 used for about US$95 recently. Should do fine until Mojave web drivers arrive for the GTX 1050.