at 300k miles, with the engine out, I'd consider the following:
head gasket
head clean / inspect
valve stem seals (the likely source of your oil consumption)
new valve cover seal / spark plug tube seals
oil pump cover seal
oil cooler seals...
if your going to do the injection pump yourself get the kit from a diesel injection shop they sells denso, there is a kit unlike from toyota. If your going to have a shop build the pump then let them buy the parts for it.
You need to do an evac and recharge, that's the only way to verify the system has the correct refrigerant charge. After that is known and it's still not working then the diagnosing can begin.
doomsday diesel has done a lot of back to back compressions with different holset turbos on his OM617 swapped into his 4runner. https://www.doomsdaydiesel.net/_files/ugd/a007e9_abf49dfb608644ca813b2b26d4f0ff18.xlsx?dn=Turbo%20Testing%20OM617.xlsx...
It may be that it works fine but the ports just don't line up like I wish they did. I'm going to try a Holset HE250WG with a 8cm twin scroll housing. if it's too laggy i have a 6cm one I can put on also.
thanks, there could be many reasons then. start at the basics. disconnect both batteries charge all the way with charger then test. once you have determined you have charged batteries that pass a test. you'll have to go tough removing checking...
I have their T3 manifold (to run with a twin scroll turbo) its not a great fit for the 1hdt as the ports on their manifold are square as you can see in the picture the ports on 1hdt are round the bolt holes have been milled out to fit the 1hdt...
if you accidentally bent them during install then maybe. doesn't really matter at this point. you can inspect the pistons for contact when you get it open.
leave the spark plugs in the heads, turn them upsidedown and fill each combustion...