Hi George,
I noticed that he was fueling a nipple on the nacelle. My guess is that they are *production* style engines, firewall mounted, and separate tanks.
Thanks to a good friend, I finally got the Hobby Helper plans for the 1963 British NATS winner which was powered with 4 Babe Bees, had throttle control and retracts! It was published in the Aug. 1963 AM.