ORIGINAL: britbrat
The GP 61(65)... is also a better real-world engine than the 61 Pro -- being ~10% lighter & making more power & torque across a broader RPM range than the Pro....
Britbrat,
Dave Gierke, in the MAN 05/03 issue engine shootout found, the OS.65LA makes more power and behaves better than the OS.61 FX...
But this was not the case with Thunder Tiger. The Pro is a stronger and better engine then the larger GP.