Its totally wrong that PIA purchased 777s on the basis of some "american pressure". A340 is a decade older then 777 and much more maintaines hungry thanks to its 4 engines and still it has lesser range. Boeing 777 was the EXCELLENT choice PIA made.
Atleast after the blunder they made in 90s to cancel the order of 4 Boeing 747-400s in favour of 6 Boeing 747-300s that too on wet lease, 777 was the excellent purchase. And it really has helped PIA to gain some "fame" in the widebody lineup on international Airports.
As for narrow bodies, I think A320s will be much more feasable and cheaper to aquire then 737NG which in NO WAY are similar to our current 737-300s.