[Fot] Are cam followers truly "flat" for TR6/GT6?

[Scott Janzen]

The lifters I am about to put into a GT6 engine to go with a new cam,  
tested, ground and polished by a well known source, are not truly  
flat.  If I put any two face to face, I can rock them slightly, almost  
imperceptibly, so they seem to be ground with a radius.
The set I have from another engine, used one short season, also  
reground through the same source, do not rock when put to the same  
test.  Can't us these because they were run with a different cam.
Do I need to find another set of lifters to replace the recently  
reground ones with the radius?  The cam source tells me they should be  
dead flat, and that the lobes on the cam have no taper.