On the oil to the heads. After doing the crossover pipe. Why not rotate number 2 an 4 cam bearings to block the passage to the head. In the lifter valley drill a hole in the passage. then take a smaller bit an drill thru the back of the passage into the oil galley on both sides of the engine. Then tap and plug the 2 holes in the valley you just drilled. The cam bearing would be oiled thru a 1/8 hole. The heads would have a constant supply of oil and the mains would have more oil.