[Mr70]

That's a 1971 issued D/G solid lifter water pump pulley that reflects the earlier 1970 issued D/G water pump pulley,#3976060AP.
It can be used on earlier Solid lifter engines starting in 1969,but technically not assembly line correct for those years.
The #3995647AP pulley was originally issued to replace the two earlier designs,and meant for solid Lifter engines after 1970...302,LT-1,L-78,LS-6.