You are not in a position to remove the camshaft without serious risk of damage.

The use of synthetic oil costs no more than dino when you factor in the mileage that can be accrued under synthetic with this engine (6K) and the capability of the filter to go this distance (6K).

Therefore, if the cost is the same, and the risks are significant to pick out the bad lifters, your decision is simple. Drive the vehicle with Mobil-1 Turbo Diesel Truck oil for 10K miles and see if the oil can cleanup the lifters.