Want a reference to the speed of light in vacuum with a meter / second precision? Just ask Google:
c
And it returns the speed of light in m/s:
the speed of light = 299 792 458 m / s
To get the Gravitational Constant, simply type ‘G’:
G
And it returns:
gravitational constant = 6.67300 × 10-11 m3 kg-1 s-2