For Brushless P60s. Get the Rs-500 or RS500/700 Backplate. Then get the 700s series pinon. This gives you a 25mm bolt pattern, as well as a 5mm bore pinion. I like the combo plate as it gives you more flexibility down the road.

Cut the brushless shaft with a Dremel (no need to disassemble) to 14mm from the face and use an arbor press to press the pinion.

12lb Common combo is a P60 16:1 paired with NTM Propdrive v2 3536 910kv or Sk3 3536-1050kv at 6S gives you about 16-18Fps

30lb Common Combo is 16:1 P60s paired with SK3 4240 or NTM 4238

5s or 6s Lipo with at least 50a ESCs. Blue Series 50a and ZTWs 50/60s have been proven to work. 80a recommended for the 30lbs.

Base Simon K settings:
RC_PULS_REVERSE = 1
RC_CALIBRATION = 0
MOTOR_BRAKE = 1
BRAKE_SPEED = 8

Additional comments:
If you have weight you can get the Steel ring gear. At $5 I think its worth the security.

Also, the gearbox bearings are 3/8" So the 1/2" shaft is 3/8" through the gearbox, but necks up after it exits the gearbox. I recommend getting the 3/8" shaft since the wheel shaft is essentially only 3/8" inside the gearbox. Save some weight.

Cheaper to buy the Mobil XHP222 grease from McMaster and very easy to grease yourself. Just add a pea size to every stage as you reassemble.
https://www.mcmaster.com/#1416k14/=19vu8g2