The thrust plate itself can be installed either side to either side, lol. The grooves are to retain a little bit of oil.
For the 56 motors, you also need to use the ring spacer. If you look at the spacer, one side has a bevel. The beveled side goes toward the can shaft (to accommodate the fillet on the cam from the machining). The spacer itself is designed so that the can gear is installed right to the spacer, no clearance needs to be checked. Install the gear firm against the ring spacer and you are done.
Feel free to put the little divots in your plate. Just don't go haywire. Dress them down nice and smooth.
If you are using an aluminum cam gear, don't press the gear on, hot or cold. Do a You Tube search for Tom Lowe's 12bolt.com video on installing the gear. Essentially you spray a little flat black paint on the back side of the gear, heat the gear up with a hand held torch to 475, put the gear on the cam and use a good size dead blow hammer to wack it on, let it fully cool.
Now, full disclosure, I just installed a gear this way a couple of weeks ago and it did not quite go all the way on, just a little smidgen short, so I put it in a press, still hot, reheated it to 475, and just nudged it down a tiny bit to firmly seat it on the spacer.
