Greg,

6001 was for the forged crank rods, if memory serves right, and the head on the pressed in stud is a bit abloid
and tends to "cock" the stud at an angle if the rod material hugs the hole, this can make pulling the caps and reinstalling
a bit tough without a tool...the 6002 has a head that is more round and fits better in the cast crankrods due to the narrow width...
but these also can be used in the forged crank rods if the material hugs the hole...