If you run any mechanical cam (solid lifter) personally I feel adjustable rockers are required. You could go thru and measure every push rod and have it be specific to where it needs to be, but there is absolutely no way to adjust lash to compensate for wear. What was the reasoning for putting the 516 heads on in place of the 906's? If it ran that well before hand or was there a thread somewhere else about it all? As far as The purple shafts, not saying they are bad, but unless I had one on hand I'd do something different but that's me. Sounds like you want a nice cruiser, which is cool, but gotta remember with solid lifter cams there is some routine up keep. A nice hydraulic will accomplish your stated goal and not require additional upkeep etc.