I'd take the oil pan off, take the oil pickup tube off, and manually clean those.
I'd take the valve cover off and throw it in the trash. The breather baffles inside are almost certainly beyond reasonably being cleaned, and how would you really know anyway?
With the valve cover off, and the oil pan off, I'd use kerosene or diesel fuel and liberally rinse it all down through the oil drain holes in the cam box area.
I'd take the oil filter/cooler housing off, take it all apart, and clean every last bit of it manually. Even better find a decent used one and use that.
Replace the turbo oil feed pipe... unless you feel reasonably sure you can get it clean. I wouldn't trust it. Take the turbo drain pipe off (inside the stand on the BRM), and make certain it is cleaned. make sure the drain fitting in the block (big banjo bolt) is clean, too.
Once you get it as clean as you can get it, put it all back together. I would fill it with oil, with a new filter, then manually crank the engine by either jumping power to the starter or disabling the engine from starting (removal of the injector plug on the head would be easiest). Crank the engine around for 20 seconds or so. Then reconnect the plug, and start it up. Make sure the oil pressure warning lamp remains off, and make sure the engine sounds like it is quieting down like the lifters are pumping up.
Then rev it to 2500 and hold it there with no load for a few minutes, shut the engine off, and drain/refill the oil and change the filter.