Paul, if the lifter are beginning to get a dish in them on their base, the cam's lobe are most likely compromised as well and the new lifters may accellerate the lobe wear. At the very leats, I would pull the valve covers and endeavor to measure the lift on each pushrod or rocker arm to determine the severity of the wear. If you can measure any differences in lift between them, time to change the cam and, unfortunately, lifters again as well.
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