90's Durango - Mechanic told friend to scrap

I helped a buddy replace the front/top end of a 4.7L. Neat engine, total garbage. Had two heads drop valve seats shortly after startup with brand-new FROM DODGE replacement heads (and both times the cooling systems was carefully refilled and the amount added measured, and everything burped with a vacuum pump). But I digress...

We had a very similar situation after getting it assembled. It would sometimes start, sometimes not. It would run for some amount of time and then just die. No noise, no clunk, nothing - sounded like keying it off. No codes, no lights, nothing. Turned out to be the cam position sensor in the passenger cylinder head. PITA to reach, but not impossible. Took 20 mins to swap and then it ran like a top all the way to the Toyota Dealer where it got traded in on a new Tundra (his buy, not mine).

I'd check the cam sensor in addition to the other simple things others have suggested (fuel pump, etc).