There's some argument about newer heads though I might be the last holdout I believe #17 was standard issue on all US 603s through 95 based on seeing a 95 S350 with original #17 head. Others say they have newer castings on cars that have never been touched. Short answer, I don't know what year #20 was standard.

All the parts different between #14 and later heads are the same for all later heads. What works for a #17 works for a #22. When buying parts, you can say anything from a 90 350SDL to a 95 S350. I don't know glow plugs by number (too lazy to check the FSM). What car are they originally for?

You can try to force the injector lines to fit. Attach them to the injectors than gently bend them to attach to the IP. Hope the lines meet the clamps.

gsxr has guidelines to machine vertical prechambers to work with later head castings. You can keep the vertical injectors, glow plugs and injector lines. You still need a couple of 80mm long bolts to replace the 50mm long bolts.

Sixto
87 300D