I'm new to the site, but not exactly a spring chicken.
If I understand your post, you want to lower your dynamic compression enuff to get by with running 87 octane gas. So, it's my understanding that you need more advertised duration. The steep ramp cams work just the opposite. They have much lower advertised duration in relation to their dur at .050 lift. Therefore, they will increase the cylinder pressure, rather than lowering it.
So, with this in mind, the smallest cam I'd recommend for your 455 is a Summit 2802. It looks to have about 20 degrees more advertised dur than the Crower 60916 you mentioned. That should lower your DCR considerably. Will also be a lot cheaper.
Now, for me personally, I would not even consider anything short of a RA4 grind, with Rhoads lifters. But some guys hate the thought of the "old school" RA4 / Rhoads combo and can't stand the "ticking" sound the Rhoads make at low rpm. If you are one of these guys, then the Summit 2802 may be your best bet. IMO If I'm wrong, it won't be the 1st time. I would also consider running 91-93 octane gas. It's not that much higher.
