When I took my seats completely apart, I didn't mark the bottoms for L/R. It is possible to switch them up when you re-assemble them. The only difference is the side that the seat adjustment lever ends up sticking out from. The attached pictures are of my drivers seat. The seat adjustment lever is coming out on the right side. Can someone check their car to see if I got it right. I have a feeling its backwards.
BTW, the white leather upholstery and seat cushions from ClassicDatsun look great. Since I don't have the car back from the shop yet, I set the seat in my living room. It looks like nice furniture, and is very comfortable. They also have more side bolstering than the old worn out ones, which keeps me in my seat better when my living room takes corners. Even better, they smell good.
Thanks.