81/82 300D/SD transmission oilpan
 

I had the transmission serviced, fluid filter change.

Now, same as with the 300D, the SD showed an out of level rim on the old tranny oilpan when it came off. The center attachment points where higher then the outer 2 bolt-on points on either side.

I wonder if this is a deformation that takes the oilpan out of spec and creates a risk for a leak down the road, or is that the way it goes after the pan is bolted to the tranny and the pan can be reused without issues?

The flanges near the bolt holes should be the same height, roughly. Most likely the bolts were overtightened at some point causing the distortion you see. The flanges should contact the transmission case and allow the rubber gasket to compress just enough to seal properly. My 560 has a trans pan distorted like this, but it's not bad enough to cause a fluid leak. Keep an eye for leaks, and replace the pan if needed.