Joe - one lesson I learned was: A solid lifter cam in a non side oiler block (designed for hydraulic lifters) will have low
oil pressure issues, unless the gallerys to the lifters are blocked off. This requires tapping the bottom of the cross gallery to the cam followers and inserting special plugs.
If this is your set up and this is not done, I'll bet this is the problem.
Let me know if you want more info on this.
Bruce