Are you daydreaming??? airlifted??? WOW.... Even those soviets will be surprised that where this nut comes from. Oh, I know. it is from india.
Believe it or not, airplanes existed by this time, and it was possible for the Soviets to airlift supplies into Vietnam. The VVS had the world's largest fleet of transport aircraft.
The majority of Vietnamese tanks, fighters, infantry weapons, SAMs, AAA, etc. were of Soviet origin. Considering most Chinese weapons were poor copies of Soviet weapons, why not just get the original thing?