p1 is always 0 in R* scripts; and a quick disassembly seems to indicate that p1 is unused.
List of component/props ID:
gtaxscripting.blogspot.com/2016/04/gta-v-peds-component-and-props.html
This is the server-side RPC native equivalent of the client native SET_PED_RANDOM_COMPONENT_VARIATION.