What cam with stock springs

You are limited to something at or less than .480 lift WITH 1.5 ratio rockers, this work out to .320 lift AT THE CAM; with the Magnums 1.6 ratio rockers you get .512 lift at the valve. At about .525 lift at the valve, you have collision issues with retainers and guides, coil bind. Those are the physical limitations, I'm not sure how well stock springs would maintain valve train control, they might be just a little weak.

To gain peace of mind, you might want to trim the tops of your guides and put in a set of R/T springs.

Others may have differing opinions.