The Spruce Goose cruised at 175-178 MPH for 3,500 miles with a full payload (130,000 lbs).
Unfortunatley, the maximum load you can carry in WITP:AE in a plane is 65,000 lbs.
But, I do have SACs for a lot of stuff:
XR6O-1 Constitution SAC -- several MB!!
And on Page 5 of the SAC they have a range/payload graph flying at an altitude of 1500 feet; which is applicable I think to the SPRUCE GOOSE.
It comes out as:
20,000 lb payload: about 2,200 nm (50% design payload)
40,000 lb payload: about 1,200 nm (design payload)
So if we assume the SPRUCE GOOSE had the same performance gains/degradation as payload increased/decreased as the R6O, then flying at 65,000 lb cargo weight (50% of design); would give the Spruce Goose a range of about 6,400 miles (or 5,560 nautical miles).
So in game the Spruce goose would be:
Max Speed: 220
Cru Speed: 175
Endurance: 2194 (minutes at cruise)
Manouver: 5 (it IS huge after all)
Climb: 500 (fpm)
Max Alt: 12000
Max Load: 65000
Service Rating of 20-30
Rng Max: 5600 (ferry range; I would imagine if you deploy a Spruce Goose somewhere, you want to carry not only the crew -- 18 men is about 3,600 lbs alone; but also some spares, mechanics, etc.)
Rng Ext: 5800 or 6000
Rng Normal: 5560
I think that should work for it.