Are you sure it's not a #14 head? If the injectors are good, why not use them? IIRC the nozzles are the same and that's where the magic happens. There's nothing inclined about the injectors themselves. If it's a later head, it'll take a very keen eye to know if the head was clearanced for early prechambers rather than the other way around. I imagine the prechambers were clearanced because it's a heck of a chore work in the prechamber pockets.

Manifold and turbo studs can be removed. Lots of penetrant, heat and a couple of nuts

Sixto
MB-less