I remembered wrong, but was close though
1Kz setting because those Jaycar SSRs don't go any faster, 1x pump per SSR with flyback diodes & heatsinks. In saying that, the heatsinks are overkill. Just on an alloy plate is more than sufficient. You'll find without a flyback diode, your SSRs will heat up big time and also die prematurely.
I've been running the two same SSRs since the last motor, no issues, car does 2 hour straight drives in summer once in a while and gets punished on the track. Nothing melts, no hot messes, etc.