for the .557 cam the mopar spring recommended is P3412068 https://www.manciniracing.com/mopupto620li.html but depending on your valves you might need something different.

On my iron heads I have .100" longer valves so the installed hgt. is more, we went with a Pac spring ( I think 1208, have to ck my notes)and retainers to achieve similar specs to the 068 spring.