The 75 MPC shows no gaskets for 69 or 70, only the one you list, and D1ZZ-6344229-A for the LH, and they're for 71 and up. However, NPD shows their 44228-1A gasket pair as replacements for 69-73.
Jim
Kind of. By 1975 the only gasket serviced was the 1971 version, D1ZZ-6344228-A (LH) and D1ZZ-6344229-A (RH). However, if you look at the spoiler kit (44210) for 69 & 70 you will notice that the D0ZB-6344228-B and D0ZB-6344229-B were included as part of the kit; but not sold separately. I would think that it is safe to assume that there was a C9 version to start the 1969 model year with.
***update - I see that on the following website they sell a reproduction of the 1969 version and claim that they are different than the 1970 versions currently reproduced.
https://www.musclecarresearch.com/6344228-1The 1970 diagram shows the gasket and mounting hardware as "serviced only in kit 44210".
To answer the OP, I would say that it is pretty clear. You have two 1971/72 (possibly 73) rear spoiler gaskets for the LH side. The RH side is different, so unfortunately you do not have a matching set. These are not correct for a 1970 (or 69). However, I can't say if the use of the D1 parts or the NPD reproductions would be obvious or not. I would think that trying to use two RH versions would be apparent.
A year or two ago I sold two used ones, with embossed numbers D1ZB-6344228-AA.