The good news:
the other week I installed Superior Shift Correction Kit springs on my '85 300D (231K miles). Completed cured the heavy slipping that had been occurring on heavy throttle 2-3 and 3-4 shifts. I can now do full throttle runs and let it wind up in each gear keeping my foot right to the floor and I get nice smooth shifts without feeling like I'm going to burn up the clutches

The bad news:
occasionally, after full throttle runs like this, when I stop and get going again it's like the trans is stuck in 1st gear; it just doesn't want to go to 2nd. Sometimes stopping again, putting it into R or P and then back to D and trying again it will return to normal. This AM even that didn't work, and I finally got irritated and just mashed the throttle and got a shift to 2nd then all was OK.

I hadn't noticed this trouble prior to installing the shift kit springs. But, since it always goes away and returns to normal shifting I'm assuming it's not a major problem, maybe an adjustment. This morning it occurred to me maybe the kickdown switch is sticky? Would that present this kind of trouble? It also looks like I might have overfilled the fluid level a tad, any chance this could do it?

Yes, sticky kickdown switch would do that, as would a sticky bowden cable. My money is probably on a sticky bowden cable. Now that you're not worrying about burning up the clutches, you're really putting your foot into it and the bowden cable is in a place it hasn't been in a while, causing it to stick sometimes.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

Thanks for the Bowden cable tip. I keep seeing mention of this in the forum but have no clue what it does. Connects from throttle linkage to trans? What exactly does it control? If it is in fact "sticky" can I lubricate it your would a regular cable that slides within a sheath?

Also, unless it is a stuck kickdown switch, the need to stop and cycle through park and reverse to get your tranny to shift out of first is also an indicator of low transmission fluid. Check your level and see if it helps.

As far as the bowden cable goes. What it does is adjust the shifting point on the transmission, relative to the physical location of the throttle. So basically, if you are deep in the pedal accelerating, it won't shift until much later since it assumes you are accelerating hard. The shorter the cable (effected by unscrewing the white adjustment nut, like the brake adjustment on your bicycle) the farther out of the pedal you'll have to be before the transmission wants to shift. This gets further complicated by the vacuum supply adjustment and trasmission vacuum modulator pressure adjustment. Once you understand the system you can tune it for your preference and to make up for wear in the system.

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'79 300D, Ivory "Gunther" ......going
'81 300SD, Metallic Blue Silver, The Grey Ghost.....going
'87 300D Turbo ...gone
'05 CDI.... gone