Bummer, sorry to hear.
Most likely would be head gasket. All the symptoms you described point to a progressive head gasket failure. The HG would have begun to leak and allow cylinder combustion pressure into the cooling system, causing pressures to spike dramatically and aerate the coolant causing the sudden overheating of the engine, and oil leaked into the coolant at the same time. Then once you're starting to get combustion gases into the coolant while still running the engine with a load, you get into a feedback cycle where the engine is getting rapidly hotter and hotter, that makes the HG fail worse and worse, more and more gases and oil go into coolant, the cooling gets even less effective and the engine heats up even more, and so on, until you pull over and shut it down.
Note that you said the hose burst after the engine overheated so the hose failure was a result of the overheating, not the cause.
Guessing you were headed up I-70 when this happened or climbing some other long steep hill on a warm August day?
Could be something else, but not very likely given the situation you saw. Oil cooler failure could introduce oil into the coolant also, but it would not result in overheating, at least not sudden overheating.
On a freshly overhauled engine like yours, headgasket failure in a short time would most likely be from one (or more) of these 3 causes:
- injection and/or cam timing not set correctly, resulting in excessive cylinder pressures
- cylinder head bolts not torqued correctly or not retorqued, or if studs were used, incorrect torque procedure or lubricant etc, OR using a clicker-type torque wrench for installation rather than a strain gauge or beam type wrench
- cylinder head warped or incorrectly machined during overhaul or insufficient surface preparation
Any built in vulnerabilities like these can be hidden when cruising around town but will be uncovered the first time the engine sees a sustained hard load in warm weather. With a heavy Pinz in the Rocky Mountains in the summertime, the stakes for engine and cooling system perfection are high.
The headgasket failure can be confirmed with the "bubble test" or a block test to check for hydrocarbons in the coolant. You can also do a pressure test of the cooling system after replacing that hose but be careful as this can forced coolant into the cylinders if the HG is indeed failed, and result in hydraulic lock and bent connecting rods/cracked pistons if you attempt to start the engine afterwards.