Just been there and done all of that with my 56 pass 235 too. I had some worn valve guides and that was the majority of my upper end noise but there was hydraulic lifter tap I had. I removed it by cutting a small groove in the ball of the pushrod ball. Lifter gets some air trapped in it and it can't get out. Talk to pre68dave on this forum, he may have a pic, but basically cut a small groove from the center of the ball on the pushrod to the outside of the ball, just a few thousands deep. Cures the tick. Here is a vid of my idling 235
1953 Chevrolet 3100 261 cu inch, sm420, 3.55 rear, torque tube still,omaha orange, still 6 volt, RPO green glass, side carrier spare, all done In the DITY Gallery Video of the 261 running
1964 GMC 1000 305 Big Block V6, sm420, the next cab off restoration
