First off, my mistake it was CFM 56-2's that they wanted to install NOT Jt 8 d's this was in 1981/82 -The Source of China re engining story is Ian Allans book by Max Kingsley - Jones, Classic Civil Aircraft Vol 5 'Hawker Siddeley Trident',(page 72) published back in 1993 it is still IMHO the best book on the Trident,still available occasionally on Ebay etc
Nothing came of the plan,just as well as China was experiencing the same wing crack problems as BA,with 2 CFm's giving about 12000lbs more thrust than 3 Speys!
Agree it seems a pointless exercise but they must have thought there was life left in the airframes,suppose we will never know..
Regards
Dave