#14 (OE US 3.0) head castings take a specific prechamber that takes a specific injector and slotted lockring. Likewise, #17 (OE US 3.5) -22 head castings take a specific prechamber that takes a specific injector and splined lockring. A 3.0 prechamber can be machined to slip into a #17-22 head. The only reason to do this is to avoid the cost of obtaining 3.5 prechambers and injectors.

Ideally, get the cam and cam towers with the head if only because of 1-2-300K miles of wear on the bearing surfaces. On a budget, who cares? The main head bolts are the same so there's no need to replace yours if they're in spec. You'll need the pair of longer bolts that go into the front cover. Nice to have OE bolts but anything you find at the hardware store that fits will work.

Make sure you get a 3.0 head gasket like you mentioned. About the only part that you can't/shouldn't use in the swap is a 3.5 head gasket. Oh, and the glow plugs. Use glow plugs for a 3.5.

There's no reason to replace the chain unless it's elongated beyond spec. If you need a new chain, replace it before or after messing with the head, not during the head swap. You don't need more variables if you're doing this for the first time, and the only step in common to the jobs is pulling the valve cover. To be clear, replace the chain, get the car running properly, then swap the head; or swap the head, get the car running properly, then replace the chain.

At least have the replacement head checked for flatness. Even a seller with the best intentions might not know if the head is warped.

If you fit new valve stem seals, use only genuine MB seals. Some aftermarket seals are known to leak and the price difference isn't worth the risk of that PITA of a job. Heck, it isn't even an easy job on a bench!

Despite what the FSM says, don't use a magnet to remove the lifters. Magnetized lifters will trap ferrous particles circulating in the oil. Use a suction cup like a valve lapping tool.

The 3.5 temp sender has an additional pin for an afterglow relay. I *think* it'll work with an early gauge if you change connector shell and you'll be ready for an afterglow relay upgrade.

Sixto
MB-less

thank you so much for the detailed reply! am getting this head at a local junk yard that is owned by one of my dad's friends so i want to get everything i could need the first time. i won't be paying any more if i leave the injectors in it, glow plugs, cam or anything like that. and thank you for clearing that up on the timing chain. i won't mess with that yet. very cool about the afterglow setup! i'll grab the relay to mess with later if it's there. are there any threads on 603 head removal and or installation? i'm on my own removing the head and haven't done it before so things like "remove the lifters" are good to know haha! and to clarify, leaving all the 3.5 #22 injectors, pre chambers, glow plugs, and injector lines will all be good upgrades? will the angled injectors have any power improvement or allow for better mpg? and the cam and towers should be gotten with this new 3.5 head as well?

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83 300CD- sanden, dual p/f condensers, 160a alternator, ect
91 300TD- 722.6, #22 head, 3.5L IP, w140 manifolds, ect

http://www.startekinfo.com/StarTek/outside/12264/Program/Engine/602_603/01-5800hx.pdf

If it's really a #17-22 head, the injectors will have to come out so you can get the bit squarely on adjacent head bolts. Bring a proper injector socket or the deepest 27mm/1-1/16" socket you can find. A 12pt socket works best. Don't turn the wrench flats higher up than the 27mm hex on the injector body! You'll need new heat shields/seals when you reinstall the injectors.

If cost isn't an object, grab the IP as a spare.

I can't tell the difference in performance or economy between vertical and inclined injection.

What kind of car has the head you're after?

Sixto
MB-less