I would shelve that engine for now to keep things simple. On the chassis, I guess my question is what seems to be missing?
Do you know what engine types are permitted for the autocross events you’re running?
Brake fluid, most likely it’s got DOT 3/4 glygol in there, in which case RBF600 would be fine to flush with as it is the same.
I would verify what type is in there first, just in case someone converted the system at some point: