Purple Cam Design Question

"Ultra-Dyne Harold" is a valve control wizard...
From what I know, a few of the MP cams were altered in the 90s. The lobes were not. The lobe timing was... The lobe shape of an MP is nothing special, which is half the reason they are considered old-school now. Bear in mind, I'm not saying they are poor designs. They are poor executions of a good design, and better more modern profiles exist now. Both because of more modern understanding of valve motion and airflow, and because of better equipment to grind more accurrate shapes. If you have some grasp of cam design and how the valves need to be worked, you can compare the different lobes and see big differences between older designs and newer ones. MP has never altered the lobes. They did change the LSA on them, and guys have also figured out that they like to be in advanced beyond what MP recommended.
As far as using the ".850" figure.. That's simply a percentage that lets you have an idea where the duration at .050" is on a medium performance level cam. And most cams if you simply multiply the advertised duration by .850 (85%) you will get close to the manufacturer's duration at .050. The more you get away from mid-level performance (smaller or larger), the more skewed the result that the ".850" figure generates. Plus, with a modern design, the opening rate is different than the closing rate. The ".850" deal assumes the lobe is symmetric. Think of it as running an engine design through a simulator program vs running a real engine on a dyno. It's ok for an idea of trends, it's not a good way to make a cam choice. If you want to see the big differences in lobes, get the lobe catalogs for the manufacturer you are thinking of using and review the other stats they give you. Or better yet, physically profile some of them. Someone on this board profiled a few MP grinds at some point... I cant recall who. Maybe they can post one of them.