I let my 79 300SD go and wish I had it back. Small pic still in my signature.
I had a gem. 9 of 10 exterior & 9.5 of 10 inside.
Problems I had were a small leak in the A pillar on highway speeds in Florida monsoon rains. AC eventually gave me problems which I have no patience for, and yes I was spoiled by my '83 which had the 6 way power driver's seat.
Still wish I kept it. Someone here told me when I got mine that driving a 79 SD on the highway was like "dancin' with a fat lady".
If you own one you know how true that is.
..