Thanks Flight Detent,
I was a bit unsure of just how much more power the P3 versions of the Allison produced. The L188 was 3750 HP per engine, the 4600 HP per engine you mention is additional 850 HP per engine / 3400 HP per aircraft. I would think that this would more than compensate for efficiency losses at high altitude, whilst optimising performance at the 'mission optimised' low level.
Regards,
Smokey