I knew Challengers were tail heavy, but not that much!
Basically every aircraft is going to have a weight and balance document, with actual weight scale readings in it, one for each gear. That is exactly what you want.
But if you are designing the facility as, say, the architect and not an aircraft engineer working an "odd job" for the hangar you work at, you probably won't have much access to such information. Here is a source for what might be your limiting factor:
and this will refer you to FAA documents on airport design. The concrete is one thing but the aircraft is going to be towed over (and perhaps parked on) rain grates and manhole covers.
Jane's World Aircraft is another excellent source; it is not only going to have weights, but wingspans, tail heights, and turning radii (be aware there can be different radii for turning under power while taxiing, and a tighter one while towing). The figures shown are close enough to scale as required and do hangar stacking.
Using 50% on each gear would be good enough; say maybe 75% to be safe for left/right asymmetry, as when removing an engine. Also be aware that aircraft will rise up as weight is removed, and the tail can get alarmingly close to the ceiling. Might not be a bad idea to check how high the nose will go when you remove the last 5% off the nose of your Challenger.
Some aircraft, namely Boeing and including the Challeger I believe, do have a "facilities planning guide" which discusses everything you need.
