Right- just block the cam tower holes. I've done several motors like this with no problems. If it doesn't drop oil pressure excessively, you can use the cam oiler in addition to the internally oiled cam.
Hi Chris--------------Speeder is right--you can use both the spray bar and the internally oiled cam together. In fact, this is a recognized setup for Nissan 4 cylinder race engines. The drop in pressure isn't enough to consider, and the top end oiling is a lot more efficient. Actually, the addition of an oil cooler will cause more of a drop in pressure than retaining the spray bar. FWIW