I do not think there are any current or new fuel efficient engines in the 43000lb thrust range - ?
The CFM Leap only goes to around 32000lbs
afaik
The RB211 535E4 was a great engine then a jump to the Trent 500 (both now too guzzley on fuel)
The new 220-235 seat A321NeoLR with ACF and Leap engines
is close to a 757 but not quite...