PU-490 was the original in-house designation for the humbucker.
There was no differentiation between pickups intended for bridge
or neck positions. This applies to all Gibson humbuckers up to
certain early '70s models.

Now they have the 490R, which is in theory electrically the same,
but made with modern materials. The 498T is a higher-output
version with wider polepiece spacing for bridge position mounting.

The 496R & 500T pickups have ceramic magnets and more
output. These are intended for use with heavy distortion & many
people find them harsh through clean/mildly overdriven amps.