This is a case where having a service manual is essential. In the '90 service manual the standard (LE) cluster is described in section 8A-80 and the SE/SSE (with and without DIC) is in section 8a-81. The connector pinouts are on 8a-80-8, 8a-81-18 - 20 .
At a quick look the connectors are the same but the connections are different e.g. LE A6 is ground while SE/SSE A6 is the SES light.
Since many of the cavities in the LE connector do not have connectors in them (eg A3-A5) it might be easier to splice in the lateer harness side connector as well or at least know how to R&R the connectors in the cavities.
So possible, not difficult, but will require some ability to rewire.