What lifters did you buy? OEM or aftermarket?
Heard some pretty bad reviews on some of the aftermarket ones (Enginetech to be specific). I have a set of those that came with the motor my brother bought for his project and he passed on to me. I'm going to go OEM at some point even thought it is $560 before tax or shipping.
I would guess that the suggestion to replace the cam is more due to the idea that a lifter might have failed and even if the cam looks ok, better safe than sorry. From the factory standpoint, better to replace a part instead of having the rig come back for further work because it wasn't. If there wasn't a failure, I would run the old cam with the new lifters and move forward. But maybe someone else has better knowledge on that.