The Israelis would get directly behind and slightly lower. The field of view in that aircraft is very limited.
Most notably, at roll rates over 180 deg per sec the 21 had a very pronounced yaw coupling that got worse as the roll rate increased . Much worse. This was largely fixed in the MiG 21Bis by using a yaw damper in the controls but it really crippled the older models in a dog fight because it prevented the pilot from taking full advantage of the 21s high relatively high maneuverability
A well flown MiG 21 bis actually has an edge over the early F16 at speeds below 400 knots, but very few jet pilots would consider engaging an enemy fighter below 400 knots
Not a very technical observation, but I always thought the MiG 21 was the neatest looking fighter. I was very excited to finally see one close-up at a museum a few years ago. I was surprised at how small they are.