If you've had this many cam issues with this block, something else is wrong. I'd lose the block before assuming its the cams fault, and investing in an even more costly cam setup in the same block.

I think the cam loss this time around is strictly due to the new lifters failing to mate properly to the cam. The first cam loss was probably my fault, and I've used this current cam since then. It even went back in after blowing it up once and has given no issues. I decided to go with new lifters (Ferrea tool steel with the EDM oil hole) as the original MP lifters (I mistakenly claimed them to be from Comp Cams) had failed. Last year I had the pushrods blow through the disc on three. Replaced those with used ones I scrounged from a friend with no issues. I had also experienced some pushrods grief with my old .080 wall 5/16 chromoly units, so I replaced both, hoping to gain a measure of reliability.
I will take look at valve springs, but at this point I'm not convinced I need a big jump in spring pressure to run a mild roller that has a very similar profile to my current flat tappet. Ditto for the bronze distributor gear, but I'll give it a good deal of thought. FWIW I'm giving serious thought to Comp's .550 lift "street roller" that has a profile no terribly unlike te MP 528 solid I currently run. I have good valve-piston clearance now, and would maintain most of it with this cam. They also have a .575 roller that has a nice profile, but would require going back to 1.5 rockers in order to maintain a suitable vtp clearance. Has anyone here run either of those cams?

Bill, once you see a roller cam lobe of similar lift and duration compared to the lobes of a solid lifter or hydraulic lifter you will see why you will want to have the opened and closed pressures the cam maker recommends You can do more damage to the valve train when using a solid roller cam by running to little pressure, not so by running 50+lbs or more spring pressurres Same thing on the pushrod diameter and wall thickness, bigger and thicker is better and stiffer Good luck, regardless of your choices