Changing Cams

Right now my advance curve is 16*/34* at 3400 and seems to work well. And the gear ratio is 3:55 with 26 inch tall tires.
I called Comp 2 years ago on using the XE 268 cam, if it would work with my existing valve springs. They have 120# seat pressure and 300# at lift. The Comp tech that the XE274 cam would be a better fit and I went with it.
I have it tuned as well as I can, the carb transition slot is square and the idle is at 850 rpm with 15 inches of vacuum.
The timing was setup by FBO for the cam.