A B777; planning to depart SBGL Runway 10 from Taxiway AA utilized maximum thrust because they were unable to determine the point on the runway from which performance data for a reduced thrust takeoff was predicated.

Narrative

Runway 10 at SBGL is NOTAMed approximately 4;200 FT closed on the approach end. Taxiing out; we were cleared via taxiways EE-M-T-BB; hold short of AA. Once cleared onto Runway 10 from BB; there is approximately 7;800 FT remaining for takeoff; NOT the stated 8;947 FT. This occurs at the point on the runway just west of where taxiway AA intersects the runway. The problem is that Ground Control brings you up Taxiway BB; and there is no way to back taxi as the runway is only 148 FT wide; and the B777 needs at least 156 FT. If you take Taxiway AA; there is at least a 150 degree turn to get lined up with Runway 10; which might mean dragging a wheel in the dirt; or taking out a runway light. It is very poorly lit by the runway. There is no information as to where the takeoff performance data is predicated on the runway. It does not say whether or not this is from AA or BB; the only two taxiways to get you to the takeoff area of the runway. We elected to change from a reduced thrust to maximum takeoff thrust to ensure a greater margin of safety. The takeoff was uneventful and we were airborne with 1;500-2;000 FT remaining. There are two issues we found. One; there is no information stating where the shortened Runway 10 performance data is predicated. Two; there is no information in the airplane manual on takeoff distance required; which is very important; in my opinion; since that would provide a great backup to a NOTAMed change of runway length and subsequent operations.