The Gibson 498T is actually a pretty hot pickup - around 16K if I recall correctly, so quite noticably higher in output than a PG bridge model. The 490R is in the classic PAF ballpark so similar in output to a PG neck.
When I had the 498T / 490R in a Les Paul I found it very difficult to EQ my amp to get them both to sound good. Either the neck would sound woolly or the bridge would sound harsh. Not a good match. I know other people get along with them fine but they didn't work for me. Every combination of Seymour Duncan pickups I've tried over the years has worked better for me.