Like Blue Horse said, there is little difference between the two years besides that which you already know.

I would go for the '89 and here's why: At right about 13 years, everything but the engine and body on these cars begins to wear out - bushings, shocks, struts, seat foam, vinyl, etc. I know, Dad bought his 245 at about 13 years old and we spent a few years steadily replacing worn parts. Last year I bought my completely original '93 at 13 years old and I've spent the past year replacing shocks, struts, bushings, etc. and the plastic is only now beginning to crack.

An '89 in constant service has probably already had all of this stuff replaced but a '92 could still be hanging on with those old wear items ready to be a major pain in the butt and hit to the wallet.

If the level of maintenance on the two cars has been comparable, I'd go with the '89.
--
Sean Corron